I haven't tried it in buying or selling. My understanding is FB holds the $$ until the item arrives. That could get a bit sticky IMO especially with the current state of Shipping or mailing anything in addition to the buyer claiming they either 1. They didn't receive it or 2. It was misrepresented.
Myself, as a seller I wouldn't like the idea of them "holding" the $$. maybe someone with a bit more knowledge /experience will chime in