Index: wp-admin/includes/update.php
===================================================================
--- wp-admin/includes/update.php	(revision 5954)
+++ wp-admin/includes/update.php	(working copy)
@@ -35,7 +35,8 @@
 <div id="update-nag"><?php printf( __('Update Available! <a href="%s">Please upgrade now</a>.'), $cur->url ); ?></div>
 <?php
 }
-add_action( 'admin_notices', 'update_nag', 3 );
+if ( current_user_can('switch_themes') )
+	add_action( 'admin_notices', 'update_nag', 3 );
 
 function wp_update_plugins() {
 	global $wp_version;