I’ve been running the Windows 7 Beta the last month or so. Started out with build 7000, which was pretty good, and now build 7057 I think. The latter one is pretty good, but in the last few days my computer has had horrid stability issues. It would just hang every few mins. It didn’t seem like a “software” hang, as everything would absolutely freeze, and if it froze in the middle of playing a racing game, the sound would also hang. I’m on 3GB of RAM, 2GB of matched pair, and a 1GB stick that I got from somewhere I don’t remember. I took the 1GB of RAM out thinking, hey, worth a shot as the first line of troubleshooting. Halfway surprisingly, it fixed my problem, but DAMN my computer is a dog now. Windows 7 itself seems a bit slower, I guess it really liked that extra 1GB. Also, surprisingly, the racing game pretty much went to shit. I was getting great 60fps at 1280×1024 resolution, but with only removing 1GB of RAM, its struggling at 1024×768. Wierd. Had no idea only 1GB of RAM could have that big of a difference on system speed.
Guess its time to pull the trigger on 4GB of faster RAM. Its cheap now anyways 
