Just a status update for my fellow longtime followers of this thread:
I sent out my first LG rMBP today, to be returned back to Apple. I opted for their prepaid shipping label and would encourage anyone else mailing a notebook back to do the same.
1.) it's free for the user and
2.) the prepaid label includes a reference number that lets Apple know when you mailed it, possibly releasing your replacement build order. (Today I was told I could not have my third rMBP order released until I mailed at least the first one back. Within a few hours, that third order now shows up as being processed. I suspect, though I cannot prove for sure, that once the USPS scans the return label Apple "knows" and can automagically unlock the replacement order.)
My third rMBP is now being built and has an estimated arrival date of Aug 21-23 via 2 day shipping. Someone on here claimed to have gotten overnight shipping, but I was never offered that and was told it wasn't possible. I'm not doubting the OP of that info, I'm merely stating that I was not able to get it. YMMV.
Additionally, I can confirm that the rMBPs now ship with Mountain Lion preinstalled. My replacement unit from week 33 had it preinstalled, though my first order did not. Furthermore, though I installed ML on my first machine, resorting to an Internet Recovery yielded Lion only. I have read hypotheses about Macs getting updated for Internet Recovery once one upgrades the machine, but that does not appear to be the case. Whatever it came with, that's what you're limited to, even if you purchase/redeem ML from he MAS. A minor thing, but potentially annoying if someone has to to an Internet Recovery of Lion then has to wait to install ML on top of that.
Finally, once a rMBP is set up for return to Apple, an email apologizing for it being DOA is sent. The subject for me was "DOA Returns and Replacements (U.S,Canada,Mexico)". I can't vouch for international folks, but screens with IR are given the DOA label.
The Quest for a Samsung Display continues!
M