I just finished the MGMAT online prep course. I did the one where you can watch the recorded classroom lectures.
Overall, I think it's a really good course. I think the classroom recordings are worth the extra $$ because they cover the really difficult stuff there and leave the easier stuff for you to do on your own.
I scored in the low 600s to start and my last GMATprep was 740. I definitively attribute that to the MGMAT course.
It is pretty intensive though. I was putting in 15-20 hrs a week just to keep up with the schedule.
GMAT Club Premium Membership - big benefits and savings