Vista SP2 is officially out as of Tuesday, so unless you want to wait till June when it will begin to show up in the Automatic Update center, head over to
Technet and download today =D. Just note that you'll need SP1 installed if you don't already (and shame if you don't, you're missing out on a greatly improved OS).
Looks like it will provide better power usage, and a few performance tweaks. If you're a fan of the exFAT file system, you're now in luck. Other features added include Blu-ray burning capabilities, new wireless technology, wireless improvement out of Sleep mode, RSS sidebar gadget improvement, Windows Search 4, and overall Sidebar optimization.
I'm downloading now, and I'll probably pass the file off to my Dad who will need to upgrade as well. With the download you can get from Technet, you'll be getting the full 5 language installation pack. If you know anyone else with Vista, pass it to them after.. No sense downloading a 350mb file if you could wait till next month when it could be a bit less.
EDIT - Installed, and it seems to have provided quite a nice post-boot performance boost
