Index: includes/ajax.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/ajax.inc,v
retrieving revision 1.25
diff -u -p -r1.25 ajax.inc
--- includes/ajax.inc	27 Jan 2010 11:19:11 -0000	1.25
+++ includes/ajax.inc	28 Feb 2010 22:12:50 -0000
@@ -124,7 +124,7 @@
  *   selected automatically for the type of form widget being used, and
  *   is only needed if you need to override the default behavior.
  * - #ajax['method']: The jQuery method to use to place the new HTML.
- *   Defaults to 'replace'. May be: 'replace', 'append', 'prepend',
+ *   Defaults to 'replaceWith'. May be: 'replaceWith', 'append', 'prepend',
  *   'before', 'after', or 'html'. See the jQuery documentation for more
  *   information on these methods.
  * - #ajax['progress']: Choose either a throbber or progress bar that is
@@ -396,13 +396,16 @@ function ajax_deliver($page_callback_res
     }
   }
   else {
-    // Like normal page callbacks, simple AJAX callbacks can return html
-    // content, as a string or renderable array, to replace what was previously
-    // there in the wrapper. In this case, in addition to the content, we want
-    // to add the status messages, but inside the new wrapper, so that they get
-    // replaced on subsequent AJAX calls for the same wrapper.
+    // Like normal page callbacks, simple AJAX callbacks can return HTML
+    // content, as a string or render array. This HTML is inserted in some
+    // relationship to #ajax['wrapper'], as determined by which jQuery DOM
+    // manipulation method is used. The method used is specified by
+    // #ajax['method']. The default method is 'replaceWith', which completely
+    // replaces the old wrapper element and its content with the new HTML.
     $html = is_string($page_callback_result) ? $page_callback_result : drupal_render($page_callback_result);
-    $commands[] = ajax_command_replace(NULL, $html);
+    $commands[] = ajax_command_insert(NULL, $html);
+    // Add the status messages inside the new content's wrapper element, so that
+    // on subsequent AJAX requests, it is treated as old content.
     $commands[] = ajax_command_prepend(NULL, theme('status_messages'));
   }
   ajax_render($commands);
@@ -481,7 +484,7 @@ function ajax_process_form($element, &$f
       'selector' => '#' . $element['#id'],
       'effect' => 'none',
       'speed' => 'none',
-      'method' => 'replace',
+      'method' => 'replaceWith',
       'progress' => array('type' => 'throbber'),
       'formPath' => implode('/', $element['#array_parents']),
     );
@@ -548,6 +551,37 @@ function ajax_command_alert($text) {
 }
 
 /**
+ * Creates a Drupal AJAX 'insert' command using the method in #ajax['method'].
+ *
+ * This command instructs the client to use one of jQuery's DOM manipulation
+ * methods to insert the given HTML. The client will use the method specified in
+ * the #ajax['method'] variable of the element that triggered the request.
+ *
+ * This command is implemented by Drupal.ajax.prototype.commands.insert()
+ * defined in misc/ajax.js.
+ *
+ * @param $selector
+ *   A jQuery selector string. If the command is a response to a request from
+ *   an #ajax form element then this value can be NULL.
+ * @param $html
+ *   The data to use with the jQuery method.
+ * @param $settings
+ *   An optional array of settings that will be used for this command only.
+ *
+ * @return
+ *   An array suitable for use with the ajax_render() function.
+ */
+function ajax_command_insert($selector, $html, $settings = NULL) {
+  return array(
+    'command' => 'insert',
+    'method' => NULL,
+    'selector' => $selector,
+    'data' => $html,
+    'settings' => $settings,
+  );
+}
+
+/**
  * Creates a Drupal AJAX 'insert/replaceWith' command.
  *
  * The 'insert/replaceWith' command instructs the client to use jQuery's
Index: misc/ajax.js
===================================================================
RCS file: /cvs/drupal/drupal/misc/ajax.js,v
retrieving revision 1.10
diff -u -p -r1.10 ajax.js
--- misc/ajax.js	3 Feb 2010 08:23:12 -0000	1.10
+++ misc/ajax.js	28 Feb 2010 22:12:50 -0000
@@ -93,7 +93,7 @@ Drupal.ajax = function (base, element, e
     selector: '#' + base,
     effect: 'none',
     speed: 'slow',
-    method: 'replace',
+    method: 'replaceWith',
     progress: {
       type: 'bar',
       message: 'Please wait...'
@@ -323,6 +323,12 @@ Drupal.ajax.prototype.commands = {
     var method = response.method || ajax.method;
     var effect = ajax.getEffect(response);
 
+    // 'replace' is deprecated in favor of 'replaceWith', but continue to
+    // support Drupal modules using the older method name.
+    if (method == 'replace') {
+      method = 'replaceWith';
+    }
+
     // Manually insert HTML into the jQuery object, using $() directly crashes
     // Safari with long string lengths. http://dev.jquery.com/ticket/3178
     var new_content = $('<div></div>').html(response.data);
Index: modules/field/field.form.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/field/field.form.inc,v
retrieving revision 1.42
diff -u -p -r1.42 field.form.inc
--- modules/field/field.form.inc	12 Feb 2010 05:38:09 -0000	1.42
+++ modules/field/field.form.inc	28 Feb 2010 22:12:51 -0000
@@ -220,7 +220,6 @@ function field_multiple_value_form($fiel
           '#ajax' => array(
             'callback' => 'field_add_more_js',
             'wrapper' => $wrapper_id,
-            'method' => 'replace',
             'effect' => 'fade',
           ),
           // The field_add_more_submit() and field_add_more_js() handlers will
Index: modules/file/file.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/file/file.module,v
retrieving revision 1.19
diff -u -p -r1.19 file.module
--- modules/file/file.module	11 Feb 2010 17:44:47 -0000	1.19
+++ modules/file/file.module	28 Feb 2010 22:12:51 -0000
@@ -351,7 +351,6 @@ function file_managed_file_process($elem
   $ajax_settings = array(
     'path' => 'file/ajax/' . implode('/', $element['#parents']) . '/' . $form['form_build_id']['#value'],
     'wrapper' => $element['#id'] . '-ajax-wrapper',
-    'method' => 'replace',
     'effect' => 'fade',
     'progress' => array(
       'type' => $element['#progress_indicator'],
Index: modules/poll/poll.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/poll/poll.module,v
retrieving revision 1.338
diff -u -p -r1.338 poll.module
--- modules/poll/poll.module	2 Feb 2010 07:39:21 -0000	1.338
+++ modules/poll/poll.module	28 Feb 2010 22:12:51 -0000
@@ -299,7 +299,6 @@ function poll_form($node, &$form_state) 
     '#ajax' => array(
       'callback' => 'poll_choice_js',
       'wrapper' => 'poll-choices',
-      'method' => 'replace',
       'effect' => 'fade',
     ),
   );