I was glad they kept the "Emergency Shutdown" feature in Vista as some nasty component (I believe it was a certain VPN Client beta that will remain nameless) caused my notebook to go into la-la land after an uninstall. I don't know how much more cleanup the emergency shutdown does than just hitting your power switch, but I suppose this might be handy if you are remoted into a machine and can't hit that switch.

To do an emergency shutdown in Vista, hit CTRL-ALT-DEL and then (assuming the next screen comes up, it may not depending on your level of hosiery) you will notice the familiar little orange power off icon in the right corner. Hold the CTRL Key down while clicking this power icon and you will get a prompt saying "If you continue, your machine will reboot and any unsaved data will be lost. Use this only as a last resort."