I use melatonin when i need to sleep at strange hours or am havjng trouble getting to sleep but never on a regular night.

It very easy to form habits on how you sleep(ask a pothead). Dont use a drug to sleep consistently.

When using melatonin i find i often sleep 8-10 hours where i normally sleep 6-8. Also i am generally a little groggy getting up (though not through out the day)

Id say go for it, but dont make it a routine

meh

From all the people I've talked to who have taken melatonin (and my own experience), never have I heard this before.

Which part the grogginess? Me and the gf both get it but i take them to pass out before early morning flights and stuff like that.

As for habit forming i just meant In general, i have no experience with melatonin forming habits either but i know many people who cant sleep without something weed/beer sleeping pills etc. i would imagine it would be easy to form a habit where you convince yourself you need it to fall asleep. Complete assumption though