From what I have seen, there is no evidence that this actually does anything for you. Unlike a lot of suppliments though, this one does at least seem to be safe. If I remember right the problem with it is absorbtion. I don't remember much about it, but I know after reading up on it, I felt it wasn't even worth a try. I have talked to other people that think it's great though. It could all be in their heads though.
From what I have learned and experienced. The things that matter are time under tension, load, protein (in perticular whey, taken at the right time), energy/food, water, standard multivitimin, sleep, time for recovery.
creatine, it gives some small temporary gains.
steroids and growth hormone, works great but very dangerous.
I haven't ever seen other suppliments work for people and some of them are dangerous too. Well that's my thoughts on the subject anyway.