As long as you the check clears, IE you have the cash in hand, and if there some kind of registration it's out of your name, what's the worry? I've bought stuff via Craigslist that way with no problems.
I've heard, though, that it can take a long time to be sure a cashiers check clears. A money order might be a lot faster if the value isn't over their limit. Others here will know more about that than me.
