I think the effect is different for everyone. I personally have extremely vivid (and not necessarily pleasant) dreams when I take a 3mg pill. 1mg or less works great, though.
As with any medication, side effects vary. When I took melatonin, I would very quickly fall asleep but would still wake up extremely tired. I also experienced very severe depression when on melatonin, that started about 2 days after use, and ended about a day after stopping use.
I do know people that have had it work very well for them, however.
I do know people that have had it work very well for them, however.