I took them for a few months, and noticed that one pill didn't have much effect but two pills would really help me concentrate and generally be in a better mood. Could be placebo idk but I didn't do any diet or exercise changes during this period so I think it is legit.
Of course, the issue here is that I think I am allergic to something in them, because if I took two pills a day for a week straight by the end of the week I would feel nauseous. I didn't get sick if I just took 1 a day, but that didn't have any effect on me anyways so it would be pointless. And while I did get something out of taking 2 it certainly wasn't anything amazing that was worth getting sick over so I stopped.