Just started trying melatonin recently, it's been working great for me. I think it helps improve the quality of sleep too, because I've been noticing a decreased need for sleep too. So far no depression (in fact, feeling pretty happy with the newfound energy), so keeping my fingers crossed that it won't become an issue.
"That's Doctor Evil to you! I didn't go to four years of evil medical school to be called "mister"!"