I've installed it on an external HD of mine. Haven't had much use for it, but it's nifty. Clean design, similar to Vista but nicer. Seems pretty good.
Oh, I'd like to go on record here and say that I hate all the people complaining about Vista. At least give the thing a try, but most people tend to go with the reviews which honestly haven't hit home. Whenever I ask someone what they dislike about Vista they say "Well...it's like, it asks you 8 times if you're SURE you wanna do something".
Well, it does that once with certain programs, but it takes about 5 seconds to turn off as well.