The old code’s effect shows up when WP_DEBUG is true:
Notice: register_uninstall_hook was called incorrectly. Only a static class method or function can be used in an uninstall hook. Please see Debugging in WordPress for more information. (This message was added in version 3.1.) in …/wp-includes/functions.php on line 3587
I’ve been looking at the CPU load since I noticed my laptop fan going full blast. By default jQuery updates every 13 ms. The load lasts longer on slow transitions. The load is higher if you have more than one widget in transition at the same time. Those can be nudged by changing the widget timeouts in Dashboard. But changing the 13 ms. requires some code. The simplest kludge is to insert this after each <script> in the PHP: jQuery.fx.interval = 200;
NOTE: this will affect all jQuery animations.
That’s for a 200ms update interval. I’m experimenting with 50ms and it looks fine.