In theory time release melatonin can only be good as an antioxidant, not for helping sleep, though we all know how good a lot of the theory is for people like us. This is because there are two windows when melatonin can trigger or reset sleep, only several hours per day. At least that was the theory years ago when I was looking into this. So a sudden high burst of melatonin will have a much more powerful effect on sleep - but only if your body is receptive to melatonin at that time of day. Some of us who do not respond to melatonin are thought to not respond because their response window has moved ... its not where its supposed to be.
Melatonin is also a powerful antioxidant with neuroprotective properties though. Melatonin taken for this reason probably makes sense as a time released form.
Bye, Alex