After the top level post about it, I bought a bottle of Melatonin to try. I've been taking it for 3 weeks. Here are my results.

Background: Weekdays I typically sleep for ~6 hours, with two .5 hour naps in the middle of the day (once at lunch and once when I get home from work). Weekends I sleep till I feel like getting up, so I usually get around 10-11 hours.

I started with a 3mg pill, then switched to a ~1.5 mg pill (I cut them in half) after being extremely tired the next day. I take it about an hour before I go to sleep.

The first thing I noticed was that it makes falling asleep much easier. It's always been a struggle for me to fall asleep (usually I have to lay there for an hour or more), but now I'm almost always out cold within 20 minutes.

I've also noticed that I feel much less tired during the day, which was my impetus for trying it in the first place. However, I'm not sure how much of this is a result of needing less sleep, and how much is a result of me falling asleep faster and thus sleeping for longer. But it's definitely noticeable.

Getting up in the morning is not noticeably easier.

No evidence that it's habit forming. I'm currently not taking it on weekends (I found myself needing a nap even after getting 10-11 hours of sleep), and I don't notice any additional difficulty going to bed beyond what I would normally have.

I seemed to have more intense dreams the first several days taking it, but they seem to have gone back to normal (or I've gotten used to them/don't remember them).

Overall it seems to work (for me at least) exactly as gwern described, and I'd happily recommend it to anyone else who has difficulty sleeping.