Limited options and an annoying setup hamper this game.
Well, when you start, you have to set up the camera. I don't mean just switch on your X Box and make sure the Kinect is properly attached. The magic 'blue area' in which you start out your stance is hypersensitive and will ask you to 'clean out' the space a bunch of times, for no reason at all. When it finally accepts your calibrations, you'll be ready to go. You can start with Zen, which is Tai Chi and yoga stretching, or cardio box. Both of these have special counters which measure the percentage power of your moves. Beware- unless you are perfect in your alignment, you'll get little credit in the Zen poses. The cardio box is a little easier, but it likewise opens up with very few sections available. It would be more fun if there were more sections open from the start, as you'd see in a real gym.
If you really like yoga and boxing, you may want to try this game. If you're looking for something you'll enjoy playing for a long time, which will give you genuine fitness results, you may be better off looking for something else.