diff --git a/ember-model.js b/ember-model.js
index 7f399e0..856586e 100644
--- a/ember-model.js
+++ b/ember-model.js
@@ -634,7 +634,7 @@ Ember.Model = Ember.Object.extend(Ember.Evented, {
   load: function(id, hash) {
     var data = {};
     data[get(this.constructor, 'primaryKey')] = id;
-    set(this, '_data', Ember.assign(data, hash));
+    set(this, '_data', Ember.merge(data, hash));
     this.getWithDefault('_dirtyAttributes', []).clear();
 
     this._reloadHasManys();
@@ -1614,8 +1614,8 @@ Ember.Model.reopen({
 (function() {
 
 var get = Ember.get,
-    set = Ember.set,
-    meta = Ember.meta;
+  set = Ember.set,
+  meta = Ember.meta;
 
 Ember.Model.dataTypes = {};
 
@@ -1836,9 +1836,9 @@ Ember.RESTAdapter = Ember.Adapter.extend({
 
   ajaxSettings: function(url, method) {
     return {
-      url: url,
-      type: method,
-      dataType: "json"
+      url         : url,
+      type        : method,
+      dataType    : "json"
     };
   },
 
@@ -1850,16 +1850,22 @@ Ember.RESTAdapter = Ember.Adapter.extend({
 
     return new Ember.RSVP.Promise(function(resolve, reject) {
       if (params) {
-        if (method === "GET") {
+        if (/get/i.test(settings.type)) { // GET
           settings.data = params;
-        } else {
-          settings.contentType = "application/json; charset=utf-8";
-          settings.data = JSON.stringify(params);
+        } else { // POST, PUT
+          if (/json/i.test(settings.contentType)) {
+            settings.data = JSON.stringify(params);
+          } else { // application/x-www-form-urlencoded; charset=UTF-8
+            settings.data = params;
+          }
         }
       }
 
-      settings.success = function(json) {
+      settings.success = function(json, textStatus, jqXHR) {
         Ember.run(null, resolve, json);
+        if (settings.successCallback) {
+          settings.successCallback.call(this, json, textStatus, jqXHR);
+        }
       };
 
       settings.error = function(jqXHR, textStatus, errorThrown) {
@@ -1869,6 +1875,11 @@ Ember.RESTAdapter = Ember.Adapter.extend({
         }
 
         self._handleRejections(method, jqXHR, resolve, reject);
+
+        
+        if (settings.errorCallback) {
+          settings.errorCallback.call(this, jqXHR, textStatus, errorThrown);
+        }
       };
 
 
@@ -2077,7 +2088,7 @@ Ember.Model.Store = Ember.Object.extend({
   createRecord: function(type, props) {
     var klass = this.modelFor(type);
     klass.reopenClass({adapter: this.adapterFor(type)});
-    return klass.create(Ember.assign({container: this.container}, props));
+    return klass.create(Ember.merge({container: this.container}, props));
   },
 
   find: function(type, id) {
diff --git a/packages/ember-model/lib/attr.js b/packages/ember-model/lib/attr.js
index fb6fc07..8d2ca9c 100644
--- a/packages/ember-model/lib/attr.js
+++ b/packages/ember-model/lib/attr.js
@@ -1,7 +1,7 @@
 require('ember-model/computed');
 var get = Ember.get,
-    set = Ember.set,
-    meta = Ember.meta;
+  set = Ember.set,
+  meta = Ember.meta;
 
 Ember.Model.dataTypes = {};
 
diff --git a/packages/ember-model/lib/model.js b/packages/ember-model/lib/model.js
index 9a4abd3..e5f05fc 100644
--- a/packages/ember-model/lib/model.js
+++ b/packages/ember-model/lib/model.js
@@ -122,7 +122,7 @@ Ember.Model = Ember.Object.extend(Ember.Evented, {
   load: function(id, hash) {
     var data = {};
     data[get(this.constructor, 'primaryKey')] = id;
-    set(this, '_data', Ember.assign(data, hash));
+    set(this, '_data', Ember.merge(data, hash));
     this.getWithDefault('_dirtyAttributes', []).clear();
 
     this._reloadHasManys();
diff --git a/packages/ember-model/lib/rest_adapter.js b/packages/ember-model/lib/rest_adapter.js
index 133da60..eb1cf75 100644
--- a/packages/ember-model/lib/rest_adapter.js
+++ b/packages/ember-model/lib/rest_adapter.js
@@ -117,9 +117,9 @@ Ember.RESTAdapter = Ember.Adapter.extend({
 
   ajaxSettings: function(url, method) {
     return {
-      url: url,
-      type: method,
-      dataType: "json"
+      url         : url,
+      type        : method,
+      dataType    : "json"
     };
   },
 
@@ -131,16 +131,22 @@ Ember.RESTAdapter = Ember.Adapter.extend({
 
     return new Ember.RSVP.Promise(function(resolve, reject) {
       if (params) {
-        if (method === "GET") {
+        if (/get/i.test(settings.type)) { // GET
           settings.data = params;
-        } else {
-          settings.contentType = "application/json; charset=utf-8";
-          settings.data = JSON.stringify(params);
+        } else { // POST, PUT
+          if (/json/i.test(settings.contentType)) {
+            settings.data = JSON.stringify(params);
+          } else { // application/x-www-form-urlencoded; charset=UTF-8
+            settings.data = params;
+          }
         }
       }
 
-      settings.success = function(json) {
+      settings.success = function(json, textStatus, jqXHR) {
         Ember.run(null, resolve, json);
+        if (settings.successCallback) {
+          settings.successCallback.call(this, json, textStatus, jqXHR);
+        }
       };
 
       settings.error = function(jqXHR, textStatus, errorThrown) {
@@ -150,8 +156,11 @@ Ember.RESTAdapter = Ember.Adapter.extend({
         }
 
         self._handleRejections(method, jqXHR, resolve, reject);
-      };
 
+        if (settings.errorCallback) {
+          settings.errorCallback.call(this, jqXHR, textStatus, errorThrown);
+        }
+      };
 
       Ember.$.ajax(settings);
    });
diff --git a/packages/ember-model/lib/store.js b/packages/ember-model/lib/store.js
index d974785..f273129 100644
--- a/packages/ember-model/lib/store.js
+++ b/packages/ember-model/lib/store.js
@@ -25,7 +25,7 @@ Ember.Model.Store = Ember.Object.extend({
   createRecord: function(type, props) {
     var klass = this.modelFor(type);
     klass.reopenClass({adapter: this.adapterFor(type)});
-    return klass.create(Ember.assign({container: this.container}, props));
+    return klass.create(Ember.merge({container: this.container}, props));
   },
 
   find: function(type, id) {