I've used it. It gave me some of the best night sleeps. I noticed that every time I took it, I remembered my dreams in the morning, something that rarely happens to me otherwise.
Sometimes my chest felt too relaxed after taking it and I experienced mild shortness of breath, but I read that this is normal in some people.
Other than a good night rest, which is good for muscle recovery, I don't think that it has any benefits for muscle gain or fat loss.