I've given 3 stars for at least the attempt to bring Brain Training to the PSP.
However, the PSP really is wasted on stuff like this. Plus, it's not the best format for it, and it means that every answer is multiple choice (even arithmetic), which is not nearly as rewarding as coming up with the answer all by yourself.
Brain Training games are best suited for the DS and for mobile phones, and that is the way it should stay in my opinion - both those formats have the ability to quickly input an answer not from a multiple choice. Not wasting time having to select from multiple choice and simply giving the answer as soon as you know it makes a big difference to how your brain benefits from these games.
If however, it is the only Brain Training game available to you, it is recommended. It would be moreso if it wasn't for the questionable "hot brain" idea which is hardly scientific