I have taken ZMA in cycles (which is a stack of Zinc, Vitamine B6 and magnesium) up to four caps prior to sleep with low calcium levels in nutrition. After 30 tot 60 minutes after ingestion I get drowsy and suffering with lethargy. What follows is a deep sleep (similar as with cannabis, the night goes quickly since you're not aware of your turn arounds and stuff), vivid and weird dreams may occur, I find these choatic but not unpleasant, it are weird and diverse associations which make up the dream(s). It did bring up some memories I had totally forgotten about.
As for the benefits for strength athletes, the deep sleep contributes to a better recovery. Libido is definitely enhanced especially in the morning, harder erections as well. Muscle tissue seems to hold water (drink it regulary) which make them appear more round.
There may be something fuzzy with it, personally I wouldn't use it myself for a period longer than 2 or 3 months a year. It won't do any harm, but long-term use is not a favor to the liver (same goes for almost all vitamine/minerals supplements for a prolonged time of use in high dose).
And also, wait about 48 hour after the last taken cap(s) with smoking cannabis or doing psychedelics, I got some unusual tachycardia and tense when getting high from THC with ZMA in my system.