Vista Window Switching

ALT-TAB still works in Vista but now gives you live previews of what's going on in the windows. It also gives the desktop as one of the switch-to-able options.

Additionally, Vista also gives you live window previews when you hover over a button in the task bar.

Lastly, if you're running Aero, you can get 3D-based window switching. I only wish there was a way to set this as the default so it works with ALT-TAB. (If there is, let me know since I can't seem to find the setting.)