I grabbed Big Brain Academy last night and it is pretty cool so far after only around an hour of usage.
It seems to have a lot more activities to "play" when compared to Brain Age. Instead of using brain age as a measurement, it uses brain weight. My initial test scored me at 900 grams.
I like the 3 different skill levels (easy, normal, hard) each with gold/silver/bronze medal awards and the multiple "tests" per each of the 5 areas gives a lot of variety. The countdown timer as you do each test makes it more video-gamey in that the faster you are, the farther you get, but correctness seems to be the heavier factor in calculations. Graphics and sound are average -- similar to Brain Age I guess.
Seems like another solid title for the DS.