I'd never went on one until two weeks ago when I rode Dr. Doom's FearFall at Islands of Adventure. The initial launch and drop are excellent, but the rest of the hops were small. I'm looking forward to next friday, though, when I go to Six Flags New England again, and get to ride Scream! which has much larger hops.
I do, purely because they are the only rides that still manage to get my nerves going. I really build up a sweat worrying about riding one if it is one I haven't. Detonator used to scare the crap out of me but no longer does since I rode Apocolypse. Which still get's me a little nervous even now!