I discuss melatonin's effects on sleep & its safety; I segue into the general benefits of sleep and the severely disrupted sleep of the modern Western world, the cost of melatonin use and the benefit (eg. enforcing regular bedtimes), followed by a basic cost-benefit analysis of melatonin concluding that the net profit is large enough to be worth giving it a try barring unusual conditions or very pessimistic safety estimates.
Full essay: http://www.gwern.net/Melatonin
I tried it for a few weeks and didn't notice any major difference. I think I'll try again on this recommendation. Perhaps my endogenous melatonin is already sufficient, or I was a lazy self-monitor.
I would summarize:
(1) In your personal experience, 1.5mg of melatonin 30 min before sleeping makes you feel 8-hours rested after 7-hours of sleep (but 9mg is harmful)
(2) that dosage has negligible cost
That's all you really needed to say.
It's jarring to me that you so meticulously analyze the cost of dosing with melatonin; once I know a cost is below some low threshold, I prefer not to think about it at all. I'd rather you took the same care into performing some objective tests of mental capability on varying amounts of sleep, so that it really means something when you say you gain an hour of wakefulness. Of course, I'd want this blinded as well, but I doubt you have convincing placebo pills available; besides, I don't mind taking something in hope of accruing some real and placebo benefits.
If your experience is typical, then the only reason people shouldn't be dosing melatonin is if there's some long-term health detriment (I don't have any mechanism in mind; it seems unlikely).
BTW, I did wind up measuring sleep over 6 months of on/off melatonin, so I now have more than intuition for the 1-hour claim (which turns out to be more like 50 minutes): http://www.gwern.net/Zeo#melatonin-analysis