I tried it at one point, and had wicked vivid dreams/nightmares, along with an only modest improvement in getting to sleep. Less than benadryl, certainly.
If you look at the rationale for using melatonin, it is always claimed that it is a natural occuring substance, part of the natural sleep cycle, and already in your body. But the standard pills they sell are about 100X what your body normally sees! If you are going to try them, I would suggest cutting the pills in eights or quarters, to get a somewhat more natural dosage.