Go to http://ui.jquery.com/ to find out more.
A quick check gives a very good feeling. They are doing it in the purest jquery style which is clean code, few lines of code, fast loading, unobstrusive system.
http://jquery.com/blog/2007/09/17/jquery-ui-interactions-and-widgets/
This will pave the way for a more interactive, more user friendly (I hope) Drupal.