MTB is good for basic review of things and refreshers, which is all most people have time for anyways while studying for step 2. It's not enough on its own, I would use UWorld + MTB.
Side note: I think onlinemeded is better in some ways that MTB, I just didn't have time to use it. If you have a lot of time to study (like, a month or more), UWorld + MTB + OME would probably prepare you very very well.