I've been to a few spin classes and enjoyed them, but finding it hard to fit in with what I want to do right now.

Worse case scenario: You get one hell of a cardio workout. The thing I find with going to a class vs working out alone - having the music pumping and an instructor barking at me tends to push me harder, and I knew if I was 'alone' - I probably would have lamed out and gone easier by that point.