Rated 5 out of 5 stars
I love it, and have used it off and on for a few years now. Only problem I have is that I have A.D.D., and StumbleUpon gets me side-tracked a lot. lol
But seriously, I would recommend it to anyone. It's a great time-waster, a great tool for work, and it's great fun if you're just REALLY bored online and just wanna "surf the 'net".