One thing a bunch of folks have mentioned, but it is worth saying again, is that you need to have a good instructor. I have been totally spoiled at our gym, because while they are all "Spinning" certified, they don't have scripted classes they have to teach or anything like that. I had no idea until a few weeks ago that other gyms actually have scripts and set profiles that they make their instructors learn and use. Before you go sign up for a gym or a spinning location, take advantage of the "free class" coupon on the spinning website and go try a few different places out. Find one you like and then give it an honest month of going regularly and you will find out for yourself if you think it is beneficial.