WOW. It's not as snappy as Windows XP, but it's definitely faster than I expected it to be. The windows switcher is really cool. The glass came on by default, and is smooth as ever. People with the geforce 6800 and on up, I can garantee it works perfect.
After 30minutes of playing around, I'm using over 600mb of RAM, so you'll probably want to at least have 2gb to make it smooth. It's probably about 1.5x-2x as bad as windows xp. If you get along fine with 1gb with xp, then 2gb will work fine for you I imagine.