diff --git a/Code/RKManagedModel.m b/Code/RKManagedModel.m
index 3817efdb..ef734614 100644
--- a/Code/RKManagedModel.m
+++ b/Code/RKManagedModel.m
@@ -101,9 +101,25 @@
 	return @"id";
 }
 
+/**
+ * TODO: Unwind assumptions about the primaryKey
+ *
+ * Right now we make the blanket assumption that Primary Keys are stored as NSNumber values. We
+ * cast from NSStrings into NSNumbers to fix a weird bug Jeremy encountered with the subtle predicate
+ * differences causes nil return values in some cases. This needs to be better understood and the assumptions
+ * unwound.
+ */
 + (id)findByPrimaryKey:(id)value {
-	NSPredicate* predicate = [NSPredicate predicateWithFormat:@"%K = %@", [self primaryKey], value];
-	return [self objectWithPredicate:predicate];
+	id primaryKeyValue = nil;
+	if ([value isKindOfClass:[NSString class]]) {
+		// Cast from string to a number
+		primaryKeyValue = [NSNumber numberWithInt:[(NSString*)value integerValue]];
+	} else {
+		// Make blind assumption here.
+		primaryKeyValue = value;
+	}
+	NSPredicate* predicate = [NSPredicate predicateWithFormat:@"%K = %@", [self primaryKey], primaryKeyValue];
+ 	return [self objectWithPredicate:predicate];
 }
 
 + (NSDictionary*)elementToPropertyMappings {
diff --git a/Code/RKModelLoader.m b/Code/RKModelLoader.m
index 2553cc54..e1d3c234 100644
--- a/Code/RKModelLoader.m
+++ b/Code/RKModelLoader.m
@@ -30,7 +30,7 @@
 }
 
 - (BOOL)processResponse:(RKResponse*)response {
-	NSString* errorMessage;
+	NSString* errorMessage = nil;
 	RKRequest* request = response.request;
 	if ([response isFailure]) {
 		[_delegate modelLoaderRequest:response.request didFailWithError:response.failureError response:response model:(id<RKModelMappable>)request.userData];
diff --git a/Code/RKModelMapper.m b/Code/RKModelMapper.m
index 514f4a37..1eec3bdf 100644
--- a/Code/RKModelMapper.m
+++ b/Code/RKModelMapper.m
@@ -86,7 +86,7 @@
 		// Don't set the property, both are nil
 	} else if (nil == propertyValue || [propertyValue isKindOfClass:[NSNull class]]) {
 		// Clear out the value to reset it
-		[model setNilValueForKey:propertyName];
+		[model setValue:nil forKey:propertyName];
 	} else if (currentValue == nil || [currentValue isKindOfClass:[NSNull class]]) {
 		// Existing value was nil, just set the property and be happy
 		[model setValue:propertyValue forKey:propertyName];
diff --git a/Code/RKResponse.m b/Code/RKResponse.m
index 2a4551c3..3a450be5 100644
--- a/Code/RKResponse.m
+++ b/Code/RKResponse.m
@@ -1,6 +1,6 @@
 //
 //  RKResponse.m
-//  RestKit
+//  RKFramework
 //
 //  Created by Blake Watters on 7/28/09.
 //  Copyright 2009 Two Toasters. All rights reserved.
@@ -18,6 +18,7 @@
 	if (self = [super init]) {
 		_payload = [[NSMutableData alloc] init];
 		_failureError = nil;
+		_loading = NO;
 	}
 	
 	return self;
@@ -53,7 +54,14 @@
 }
 
 - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
-	[_payload appendData:data];
+	if (NO == _loading) {
+		_loading = YES;
+		if ([[_request delegate] respondsToSelector:@selector(requestDidStartLoad:)]) {
+			[[_request delegate] requestDidStartLoad:_request];
+		}
+	}
+	
+	[_payload appendData:data];		
 }
 
 - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSHTTPURLResponse *)response {
@@ -62,15 +70,24 @@
 
 - (void)connectionDidFinishLoading:(NSURLConnection *)connection {
 	[connection release];
-	NSDate* receivedAt = [NSDate date];
+	NSDate* receivedAt = [NSDate date]; // TODO - Carry around this timestamp on the response or request?
 	NSDictionary* userInfo = [NSDictionary dictionaryWithObjectsAndKeys:[_request HTTPMethod], @"HTTPMethod", [_request URL], @"URL", receivedAt, @"receivedAt", nil];
-	[[NSNotificationCenter defaultCenter] postNotificationName:kRKResponseReceivedNotification object:self userInfo:userInfo];
-	[[_request delegate] performSelector:[_request callback] withObject:self];	
+	[[NSNotificationCenter defaultCenter] postNotificationName:kRKResponseReceivedNotification object:self userInfo:userInfo];	
+	
+	[[_request delegate] performSelector:[_request callback] withObject:self];
+	
+	if ([[_request delegate] respondsToSelector:@selector(requestDidFinishLoad:)]) {
+		[[_request delegate] requestDidFinishLoad:_request];
+	}
 }
 
 - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
 	_failureError = [error retain];
 	[[_request delegate] performSelector:[_request callback] withObject:self];
+	
+	if ([[_request delegate] respondsToSelector:@selector(request:didFailLoadWithError:)]) {
+		[[_request delegate] request:_request didFailLoadWithError:error];
+	}
 }
 
 - (NSString*)localizedStatusCodeString {
diff --git a/Code/RestKit/RKRequest.h b/Code/RestKit/RKRequest.h
index 8f32152a..038213bf 100644
--- a/Code/RestKit/RKRequest.h
+++ b/Code/RestKit/RKRequest.h
@@ -100,3 +100,16 @@
 - (void)delete;
 
 @end
+
+/**
+ * Lifecycle events for RKRequests
+ *
+ * Modeled off of TTURLRequest
+ */
+@protocol RKRequestDelegate 
+@optional
+- (void)requestDidStartLoad:(RKRequest*)request;
+- (void)requestDidFinishLoad:(RKRequest*)request;
+- (void)request:(RKRequest*)request didFailLoadWithError:(NSError*)error;
+- (void)requestDidCancelLoad:(RKRequest*)request; // not yet implemented
+@end
diff --git a/Code/RestKit/RKResponse.h b/Code/RestKit/RKResponse.h
index 16afa1b7..b5b024ff 100644
--- a/Code/RestKit/RKResponse.h
+++ b/Code/RestKit/RKResponse.h
@@ -15,6 +15,7 @@
 	NSHTTPURLResponse* _httpURLResponse;
 	NSMutableData* _payload;
 	NSError* _failureError;
+	BOOL _loading;
 }
 
 /**
diff --git a/RestKit.xcodeproj/project.pbxproj b/RestKit.xcodeproj/project.pbxproj
index 0bd3d69a..110d61b7 100644
--- a/RestKit.xcodeproj/project.pbxproj
+++ b/RestKit.xcodeproj/project.pbxproj
@@ -44,6 +44,7 @@
 		256FD643112C7A5C0077F340 /* libjson.a in Frameworks */ = {isa = PBXBuildFile; fileRef = 256FD631112C79750077F340 /* libjson.a */; };
 		256FD651112C7B780077F340 /* RKMappableObject.m in Sources */ = {isa = PBXBuildFile; fileRef = 256FD64F112C7B780077F340 /* RKMappableObject.m */; };
 		256FD652112C7B780077F340 /* RKMappableAssociation.m in Sources */ = {isa = PBXBuildFile; fileRef = 256FD650112C7B780077F340 /* RKMappableAssociation.m */; };
+		256FDE55112DB0B90077F340 /* RKModelMapperSpecModel.m in Sources */ = {isa = PBXBuildFile; fileRef = 256FDE54112DB0B90077F340 /* RKModelMapperSpecModel.m */; };
 		2580B068102E0F1000832D07 /* RKModelLoader.h in Headers */ = {isa = PBXBuildFile; fileRef = 2580B066102E0F1000832D07 /* RKModelLoader.h */; };
 		2580B069102E0F1000832D07 /* RKModelLoader.m in Sources */ = {isa = PBXBuildFile; fileRef = 2580B067102E0F1000832D07 /* RKModelLoader.m */; };
 		2580B0C7102E1EBC00832D07 /* libElementParser.a in Frameworks */ = {isa = PBXBuildFile; fileRef = 3F4E18DB102DD31E00320118 /* libElementParser.a */; };
@@ -67,7 +68,7 @@
 		3F4E18F9102DD38800320118 /* RKParamsDataAttachment.m in Sources */ = {isa = PBXBuildFile; fileRef = 3F4E18EA102DD38700320118 /* RKParamsDataAttachment.m */; };
 		3F4E18FA102DD38800320118 /* RKParamsFileAttachment.h in Headers */ = {isa = PBXBuildFile; fileRef = 3F4E18EB102DD38700320118 /* RKParamsFileAttachment.h */; };
 		3F4E18FB102DD38800320118 /* RKParamsFileAttachment.m in Sources */ = {isa = PBXBuildFile; fileRef = 3F4E18EC102DD38700320118 /* RKParamsFileAttachment.m */; };
-		3F4E18FC102DD38800320118 /* RKRequest.m in Headers */ = {isa = PBXBuildFile; fileRef = 3F4E18ED102DD38700320118 /* RKRequest.m */; };
+		3F4E18FC102DD38800320118 /* RKRequest.h in Headers */ = {isa = PBXBuildFile; fileRef = 3F4E18ED102DD38700320118 /* RKRequest.h */; };
 		3F4E18FD102DD38800320118 /* RKRequest.m in Sources */ = {isa = PBXBuildFile; fileRef = 3F4E18EE102DD38700320118 /* RKRequest.m */; };
 		3F4E18FE102DD38800320118 /* RKRequestSerializable.h in Headers */ = {isa = PBXBuildFile; fileRef = 3F4E18EF102DD38700320118 /* RKRequestSerializable.h */; };
 		3F4E18FF102DD38800320118 /* RKResponse.h in Headers */ = {isa = PBXBuildFile; fileRef = 3F4E18F0102DD38700320118 /* RKResponse.h */; };
@@ -225,6 +226,8 @@
 		256FD64D112C7AF50077F340 /* RKMappableAssociation.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = RKMappableAssociation.h; sourceTree = "<group>"; };
 		256FD64F112C7B780077F340 /* RKMappableObject.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RKMappableObject.m; sourceTree = "<group>"; };
 		256FD650112C7B780077F340 /* RKMappableAssociation.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RKMappableAssociation.m; sourceTree = "<group>"; };
+		256FDE53112DB0B90077F340 /* RKModelMapperSpecModel.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = RKModelMapperSpecModel.h; sourceTree = "<group>"; };
+		256FDE54112DB0B90077F340 /* RKModelMapperSpecModel.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RKModelMapperSpecModel.m; sourceTree = "<group>"; };
 		2580B066102E0F1000832D07 /* RKModelLoader.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = RKModelLoader.h; path = RestKit/RKModelLoader.h; sourceTree = "<group>"; };
 		2580B067102E0F1000832D07 /* RKModelLoader.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RKModelLoader.m; sourceTree = "<group>"; };
 		25FCDDD91035BC85005418A7 /* RKManagedModel.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = RKManagedModel.h; path = RestKit/RKManagedModel.h; sourceTree = "<group>"; };
@@ -250,7 +253,7 @@
 		3F4E18EA102DD38700320118 /* RKParamsDataAttachment.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RKParamsDataAttachment.m; sourceTree = "<group>"; };
 		3F4E18EB102DD38700320118 /* RKParamsFileAttachment.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = RKParamsFileAttachment.h; path = RestKit/RKParamsFileAttachment.h; sourceTree = "<group>"; };
 		3F4E18EC102DD38700320118 /* RKParamsFileAttachment.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RKParamsFileAttachment.m; sourceTree = "<group>"; };
-		3F4E18ED102DD38700320118 /* RKRequest.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RKRequest.m; sourceTree = "<group>"; };
+		3F4E18ED102DD38700320118 /* RKRequest.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = RKRequest.h; path = RestKit/RKRequest.h; sourceTree = "<group>"; };
 		3F4E18EE102DD38700320118 /* RKRequest.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = RKRequest.m; sourceTree = "<group>"; };
 		3F4E18EF102DD38700320118 /* RKRequestSerializable.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = RKRequestSerializable.h; path = RestKit/RKRequestSerializable.h; sourceTree = "<group>"; };
 		3F4E18F0102DD38700320118 /* RKResponse.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = RKResponse.h; path = RestKit/RKResponse.h; sourceTree = "<group>"; };
@@ -352,6 +355,8 @@
 				3F032AA710FFBBCD00F35142 /* RKHouse.m */,
 				3F032AA910FFBC1F00F35142 /* RKResident.h */,
 				3F032AAA10FFBC1F00F35142 /* RKResident.m */,
+				256FDE53112DB0B90077F340 /* RKModelMapperSpecModel.h */,
+				256FDE54112DB0B90077F340 /* RKModelMapperSpecModel.m */,
 			);
 			path = Models;
 			sourceTree = "<group>";
@@ -422,7 +427,7 @@
 			children = (
 				3F4E18E3102DD38700320118 /* RKClient.h */,
 				3F4E18E4102DD38700320118 /* RKClient.m */,
-				3F4E18ED102DD38700320118 /* RKRequest.m */,
+				3F4E18ED102DD38700320118 /* RKRequest.h */,
 				3F4E18EE102DD38700320118 /* RKRequest.m */,
 				3F4E18F0102DD38700320118 /* RKResponse.h */,
 				3F4E18F1102DD38800320118 /* RKResponse.m */,
@@ -517,7 +522,7 @@
 				3F4E18F6102DD38800320118 /* RKParamsAttachment.h in Headers */,
 				3F4E18F8102DD38800320118 /* RKParamsDataAttachment.h in Headers */,
 				3F4E18FA102DD38800320118 /* RKParamsFileAttachment.h in Headers */,
-				3F4E18FC102DD38800320118 /* RKRequest.m in Headers */,
+				3F4E18FC102DD38800320118 /* RKRequest.h in Headers */,
 				3F4E18FE102DD38800320118 /* RKRequestSerializable.h in Headers */,
 				3F4E18FF102DD38800320118 /* RKResponse.h in Headers */,
 				3F4E191A102DD42F00320118 /* NSDictionary+RKRequestSerialization.h in Headers */,
@@ -737,6 +742,7 @@
 				256FD523112C6A340077F340 /* Data Model.xcdatamodel in Sources */,
 				256FD651112C7B780077F340 /* RKMappableObject.m in Sources */,
 				256FD652112C7B780077F340 /* RKMappableAssociation.m in Sources */,
+				256FDE55112DB0B90077F340 /* RKModelMapperSpecModel.m in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
diff --git a/Specs/Models/RKModelMapperSpecModel.h b/Specs/Models/RKModelMapperSpecModel.h
new file mode 100644
index 00000000..6c9ecd41
--- /dev/null
+++ b/Specs/Models/RKModelMapperSpecModel.h
@@ -0,0 +1,23 @@
+//
+//  RKModelMapperSpecModel.h
+//  RestKit
+//
+//  Created by Blake Watters on 2/18/10.
+//  Copyright 2010 Two Toasters. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+
+
+@interface RKModelMapperSpecModel : NSObject {
+	NSString* _name;
+	NSNumber* _age;
+	NSDate* _createdAt;
+}
+
+@property (nonatomic,retain) NSString* name;
+@property (nonatomic,retain) NSNumber* age;
+@property (nonatomic,retain) NSDate* createdAt;
+
+@end
+
diff --git a/Specs/Models/RKModelMapperSpecModel.m b/Specs/Models/RKModelMapperSpecModel.m
new file mode 100644
index 00000000..794955d4
--- /dev/null
+++ b/Specs/Models/RKModelMapperSpecModel.m
@@ -0,0 +1,18 @@
+//
+//  RKModelMapperSpecModel.m
+//  RestKit
+//
+//  Created by Blake Watters on 2/18/10.
+//  Copyright 2010 Two Toasters. All rights reserved.
+//
+
+#import "RKModelMapperSpecModel.h"
+
+
+@implementation RKModelMapperSpecModel
+
+@synthesize name = _name;
+@synthesize age = _age;
+@synthesize createdAt = _createdAt;
+
+@end
diff --git a/Specs/RKModelMapperSpec.m b/Specs/RKModelMapperSpec.m
index fa53ed4d..2d44acc7 100644
--- a/Specs/RKModelMapperSpec.m
+++ b/Specs/RKModelMapperSpec.m
@@ -128,6 +128,58 @@
 	[expectThat([[result hasMany] count]) should:be(2)];
 }
 
+- (void)itShouldNotUpdateNilPropertyToNil {
+	RKModelMapperSpecModel* model = [[RKModelMapperSpecModel alloc] autorelease];
+	RKModelMapper* mapper = [[RKModelMapper alloc] init];
+	[mapper updateObject:model ifNewPropertyPropertyValue:nil forPropertyNamed:@"name"];
+	
+	[expectThat(model.name) should:be(nil)];
+}
+
+- (void)itShouldBeAbleToSetNonNilPropertiesToNil {
+	RKModelMapperSpecModel* model = [[RKModelMapperSpecModel alloc] autorelease];
+	model.age = [NSNumber numberWithInt:0];
+	RKModelMapper* mapper = [[RKModelMapper alloc] init];
+	[mapper updateObject:model ifNewPropertyPropertyValue:nil forPropertyNamed:@"age"];
+	
+	[expectThat(model.age) should:be(nil)];
+}
+
+- (void)itShouldBeAbleToSetNilPropertiesToNonNil {
+	RKModelMapperSpecModel* model = [[OTRestModelMapperTestModel alloc] autorelease];
+	RKModelMapper* mapper = [[RKModelMapper alloc] init];
+	[mapper updateObject:model ifNewPropertyPropertyValue:[NSNumber numberWithInt:0] forPropertyNamed:@"age"];
+	
+	[expectThat(model.age) should:be([NSNumber numberWithInt:0])];
+}
+
+- (void)itShouldBeAbleToSetNonNilNSStringPropertiesToNonNil {
+	RKModelMapperSpecModel* model = [[RKModelMapperSpecModel alloc] autorelease];
+	RKModelMapper* mapper = [[RKModelMapper alloc] init];
+	
+	model.name = @"Bob";
+	[mapper updateObject:model ifNewPropertyPropertyValue:@"Will" forPropertyNamed:@"name"];
+	[expectThat(model.name) should:be(@"Will")];	
+}
+
+- (void)itShouldBeAbleToSetNonNilNSNumberPropertiesToNonNil {
+	RKModelMapperSpecModel* model = [[RKModelMapperSpecModel alloc] autorelease];
+	RKModelMapper* mapper = [[RKModelMapper alloc] init];
+	
+	model.age = [NSNumber numberWithInt:16];
+	[mapper updateObject:model ifNewPropertyPropertyValue:[NSNumber numberWithInt:17] forPropertyNamed:@"age"];
+	[expectThat(model.age) should:be([NSNumber numberWithInt:17])];	
+}
+
+- (void)itShouldBeAbleToSetNonNilNSDatePropertiesToNonNil {
+	RKModelMapperSpecModel* model = [[RKModelMapperSpecModel alloc] autorelease];
+	RKModelMapper* mapper = [[RKModelMapper alloc] init];
+	
+	model.createdAt = [NSDate date];
+	[mapper updateObject:model ifNewPropertyPropertyValue:[NSDate dateWithTimeIntervalSince1970:0] forPropertyNamed:@"createdAt"];
+	[expectThat(model.createdAt) should:be([NSDate dateWithTimeIntervalSince1970:0])];	
+}
+
 @end
 
 @implementation RKModelMapperSpec (Private)
diff --git a/Specs/main.m b/Specs/main.m
index 66c5e4ff..a1a5b61b 100644
--- a/Specs/main.m
+++ b/Specs/main.m
@@ -7,7 +7,7 @@
 //
 
 #import <UIKit/UIKit.h>
-#import "UISpec.h"
+#import <UISpec.h>
 
 int main(int argc, char *argv[]) {