The game claims to score brain development, but there is no baseline testing, so getting a high score at the start seems to invalidate the whole process. What are you being compared to when receiving a 100% score? In the end, this game lacks punch.
If you want a good, fun, and challenging way to work your mind, do yourself a favor and pick up a copy of Professor Layton. The 130-odd logic puzzles found there-in will do more for your brain than wasting time and money on a poor Brain Age knock-off.
As far as effectiveness in training goes ... I don't know. I wish it had a Brain Age kind of graph in order to see how far I've progressed. I hate to say it, but there is a strong possibility that I might be a little rustier after Mega Brain Boost than before.