If the dealer gets stuck with them, they own them, no?
Well, yes and no. Dealers have a limited amount of items they can return, and if your CDs are one of them, you don't get paid by the distro for it. This has only happened a couple times to me, though, to the tune of, maybe, $50. Of course, if distros can't get stores to buy your stuff, you don't get paid for it. What sucks is when the distro pays you, returns your unsold stuff, and bills you for the difference.
another thing that sucks is getting your damn money from these distros! They are always late!
Of the places you used, which was the best for you?
It depends on the record. For my album, the best seller was Twee Kitten. For the other albums my label has released, it's been distros like Darla, Revolver, and K. That will vary depending on what type of music you do.