Index: wp-admin/wp-admin.css
===================================================================
--- wp-admin/wp-admin.css	(revision 10948)
+++ wp-admin/wp-admin.css	(working copy)
@@ -1,4 +1,3 @@
-
 textarea,
 input,
 select {
@@ -2922,6 +2921,12 @@
 	margin-top: 8px;
 }
 
+form.upgrade .hint {
+	font-style: italic;
+	font-size: 85%;
+	margin: -0.5em 0 2em 0;
+}
+
 #poststuff .inside .the-tagcloud {
 	margin: 5px 0 10px;
 	padding: 8px;
Index: wp-admin/update-core.php
===================================================================
--- wp-admin/update-core.php	(revision 10948)
+++ wp-admin/update-core.php	(working copy)
@@ -13,6 +13,7 @@
 	wp_die(__('You do not have sufficient permissions to update plugins for this blog.'));
 
 function list_core_update( $update ) {
+    global $wp_local_package;
 	$version_string = 'en_US' == $update->locale ?
 			$update->current : sprintf("%s&ndash;<strong>%s</strong>", $update->current, $update->locale);
 	$current = false;
@@ -50,6 +51,8 @@
 		else
 			echo '<input id="undismiss" class="button" type="submit" value="' . attribute_escape(__('Bring back this update')) . '" name="undismiss" />';
 	echo '</p>';
+	if ( 'en_US' != $update->locale && ( !isset($wp_local_package) || $wp_local_package != $update->locale ) )
+	    echo '<p class="hint">'.__('This localized version contains both the translation and various other localization fixes. You can skip upgrading if you want to keep your current translation.').'</p>';
 	echo '</form>';
 
 }