This service was a game changer for me. I increased my score by 70 points from my first GMAT. I found the lessons were more specific and I was able to focus more time on those areas that I felt I needed extra practice. This allowed to target the areas that I need to improve on. After doing their list of problems, I felt their score estimator was quite accurate. The only downside I found was the rather monotonous voice that reads each of the lessons. It was very scripted and I would have to take breaks just to maintain my focus.