After playing around this weekend with Vista, this is my second post about it.

First of all, If you want to have the 3D look when tabbing between programs, you must have installed the Aero theme (which is by default enabled).  Then Don't use the ALT-TAB key combination.  This give you the old fashioned way of tabbing, but with screen preview (like the powertoy under Windows XP).  Use WINDOWSKEY-TAB to use the 3D tabbing.

If you have the Ultimate version installed, you get some extra downloads with new functionality from Microsoft.  One of the current downloads is a preview of dreamscene.  This enables your PC to have movies as a background. Follow next steps to use dreamscene :

First enable dreamscene through the desktop background section of Personalization

Now you can click on a movie (WMV and MPG) and set the movie as your background.

By right clicking on your desktop and you can pause and play again your movie.

(Images comming from My Digital Life)

BTW : If you don't have the automatic updates on you can download the preview directly from here.