Part of the problem is that there is no "official response" yet within Apple, so while the individuals you talk to may see/understand the problem, they aren't allowed to say "Yeah, that unacceptable and we should replace it for you." They may give you one replacement if you are after your 14-day window (and they sort of have to take it back if you are within your 14-day window), but they still have to toe the company's official response to all "image retention" issues, which is "use a screen saver, don't leave the same images on-screen for extended periods of time, etc." because in many cases, this will prevent image retention/burn-in on screens that only show such issues under extreme situations.
I do believe they are still gathering information on the issue and trying to come up with a plan, but they haven't finalized the plan yet. First off, they need to get the issue resolved at the screen manufacturer to stop the bleeding and because they really can't be stuck with a single supplier.
They they have to figure out how to clean the bad screens (both shipped and unshipped) out of the system and replace them with good screens. Right now they only way is for customers to play the lottery, and that's not something Apple wants to encourage. Also, many customers may have a screen that could potentially exhibit the problem, but they don't use their computer in a way that they ever notice the problem, so from Apple's standpoint there's really no need to replace those screens since those are already satisfied customers (and it isn't a safety issue like a problem with the battery).
Looking that last version of the list of good/bad screens and production dates earlier in this thread, it would appear that there are still late-production units with LG screens that still demonstrate the problem. This could imply that LG is still producing bad screens, so we are still in the early stages of Apple coming up with a solution to the problem.
Yes, it ***** for everyone affected, including Apple, but for now you really have two options that I can see:
1) Keep buying and returning your rMBP (within the 14-day window) until you get one that doesn't have the problem, potentially running the risk that they may not let you return your latest unit if you are out of the 14-day window when the problem occurs.
2) If you have a rMBP with the problem, return it and wait to buy a new one until there is some information indicating the problem has been resolved so you can increase your chances of getting a good one.
Also keep in mind that there's always the chance that Apple may end up taking the final position that the image retention issue is "not severe enough to justify repair/replacement". I can understand that they might take this position as a stop-gap measure while still figuring out what to do, but I'd be VERY disappointed if that was their final position on the matter.