The study (linked on the sourceforge site) seems to indicate that it does, at least among the general population.

Anecdotally, I've used it for about six weeks now, 25 sessions at a time, every day, and can reliably get to dual-10-back, though I have a lot of difficulty there. When I started, I had modest difficulty with dual-3-back. I would say that there has been some form of improvement -- though it's not clear if the improvement is task-specific.

I haven't noticed any significant difference in my day to day life, but (to be immodest in the name of efficiency for a moment) I had a very good memory to begin with, and I would say strong fluid intelligence. It's possible that people starting from positions of lower fluid intelligence would see a more pronounced benefit.