I justed started a bottle of ZMA by Twin Lab a week ago, with 3 pills a day, 30 mins before bed (as per bottle instructions). For me it's hard to evaluate benefits from individual supplements as I intake protein, glutamine, creatine, 19-nor-4, and ZMA daily.
Someone made a comment that they wake up on a regular basis during the night, and I have experienced that for sure. It doesn't make you wired like ephedrine, but for some reason sleep is interrupted.