I ride a ss mountain bike for urban stuff and it treats me wonderfully. I've got a friend who's a pretty talented single track racer and he swore off gears quite a while ago. If you're going to use it for a trail bike the simplicity is great, though you'll spin a lot downhill. It's never been a problem for me as long as the trails aren't too straight. It's a really easy way to shave some weight, and it's good strength training. My quads got pretty nice when I made the switch. It's pretty nice to not worry about dropping your bike derailuer first on a rock or dropping chains, too. As far as urban stuff goes I prefer it to a bunch of gears, too. Saves some weight for hauling the bike around, and I always stuck to one or two gears anyways. Plus I really suck at tuning derailluers (no skill at all). I'm kind of a newb and I've heard some pretty heated arguements against single speeds, but I really like em. Worth trying, at the very least.