I LOVE spinning
I think i've been doing it ooo... 4 years now? and I probably go at least 4 - 5 times a week. It's a fantastic workout that never gets any easier no matter how long you've been doing it. You could do any class you like, its all about how you set your resistance. We have beginers, inter and advanced all mixed together and I can tell you I get just as much of a sweat on as the person whose done one class beside me lol. Thats anothe reason I like it so much, its a group class but its still very much an individual thing.
Its been great for my legs and bum and awesome for improving cardio strength/endurance. It really helped both my running and dragon boating.