By now you're aware that the Windows Vista SP1 Beta has been released to beta testers for a thorough shakedown. I just wanted to give anyone who still has UAC on a bit of warning. If you right-click the installer and select "Run as Administrator" first, then it won't take nearly as long to extract the files. Otherwise, it takes almost 15 minutes just to fail thrugh the copy the first time, until you finally get the UAC dialog.
Also, be aware that, while it says it can take up to 30 minutes, it's closer to an hour, and it will restart 3 or 4 times in the process (checking the box at the beginning is definitely advised). I've been running SP1 on my main machine for a few hours now, and it seems to be pretty stable. I'll have more on this later.