Not about the US, but here in the UK there's no restocking fee (nowadays almost no one charges you for restocking fee), I returned my 13" rMBP for the full refund (delivery was also refunded, I paid for Saturday delivery)
Returned mine because of the image retention issue and I couldn't be bothered replacing it to only have another machine with the same issue, thought I'd wait a bit and maybe get something else, don't really need a laptop anyways, my iPad is enough for now.