The research on brain-training software can be summarized as:
1. okay at improving your skills in completing the specific activities used in the program. (e.g., digit span)
2. negligible transfer to any other task or skill, even relatively closely-related ones. (e.g., letter span)
3. no better than spending time playing video games (which, actually, there is some positive research on).
Of course, no significant harm is known, either, and any intervention has the potential to do some good for a specific individual, even if there are insignificant group effects, so if spending the money would not detract from other opportunities of value to you, it is still something to think about.
