I can definitely vouch for the effects of melatonin. They do help with lucid dreaming, and they help with extremely vivid, colorful, and WILD dreams in general. It is also a lot easier to remember my dreams if I use melatonin.
I've found that it has a downside, though. Sometimes I wake up feeling a lot more tired than I felt before I went to bed! Also, as a sleep aid, I find that I've got to hit the sack the moment I start feeling tired, otherwise I "miss the train", so to speak. As a result, I tend to use it only occasionally.
"It is only with the heart that one can see rightly;
what is essential is invisible to the eye."
-Antoine de Saint-Exupery