Funny thing is CS4 doesn't work worth s**t on WinXP for me, while CS3 works fine and dandy (I also prefer it anyway, it's not like I'm gonna use CS4's 3d painting) while on Windows 7, CS3 barely worked and had terrible lag, while CS4 worked like a charm.
for some reason it lags a little on me but i am ok with it as long as its not ruining my art but mainly i think it is cause all the things i have running at the time