Microsoft released some patches for Vista today that should help with performance.
That second one is important if you play games, and especially if you play games on an NVidia 8800 video card. It is supposed to stop the annoying lockups while playing, and the blank screen that occurs when you update video drivers.
Edit: After the second update, Vista requires you to reboot. When your computer comes back up, reboot again. If you do not do this second update, gaming will really, really suck. Trust me.