actually they were some rather unfavorable side effects, not just intense dreaming (which is more of an effect of staying in deep REM sleep)
lemmie see if I can find them...
found it!
"Most suggest links to aggravation of depression, potential retinal damage, repression of tumor-growth (a good side effect), possible links to reduced fertility. None have been priven conclusively, but it is something to consider."
a friend sent me that. What I take from it is: you shouldn't NEED melatonin as a sleep aid every day, and if you're taking it that way, it might catch up to you in a bad way.
so, like anything, moderation should prevent any complications.