Rolled the dice and had my LG screen replaced. While I was in the apple store, I did some detective work. What I observed:
(When I say brighter below, I mean at 100% brightness, white background and stock apple color calibration profile for the screen... additional brightness equavalent to 1-1.5 brightness keyboad clicks)
1. Not all retina screens are equal. Some are definitely brighter than others. I originally had a samsung... it was brighter than the 2 LG screens I've had. The 2 LG screens were equivalent to each other in brightness.
2. In the apple store I went to, the 13 inch MBPr display models were all brighter than my new LG 15" replacement display. There were 2 15" MBP retinas on display that were brighter than mine with the new LG screen.
(Tried to ID the different screens in the store via. command line, but was unable to do so due to a change in apple hardware or not having admin priv.) I wonder if the additional light output is due to a different manufacturing process with LG vs. Samsung and resulting light transmission characteristics. Suppose it could be the LED lighting. Regardless, there is a difference.
3. My samsung never had the image retention behavior. It appeared on my second replacement LG screen today after cleaning with a damp lint free cotton cloth, and then returned to normal after 15-20 minutes, which leads me to believe that it is possible that *moisture* plays a role in image retention issues with the LG screens (never had this issue with the Samsung, ...ever) Just a casual observation.
4. The second LG screen seems to need a different color calibration to achive the same results as the previous LG screen, which further leads me to believe that standardizing these screens to a level where an astute observer can't tell the difference must be currently next to impossible from a manufactuing standpoint (LG at least). The calibration is also very different from my original samsung screen.
5. It ***** to feel like I have a possibly inferior product to the one I originally purchased and to not really be able to ascertain if I do. It clouds the mind and creates doubt. When sourcing from different manufacturers, the customer shouldn't be able to tell a difference. This is very wrong in my opinion (and is obviously causing apple problems, hence this thread). The main selling point of the retina MBP is the screen for God's sake.
6. I sucked it up and bought applecare for the first time. It appears that buying applecare directly from apple is a rip at $349... did a seach and bought applecare from B&H camera, saving myself $100... got it at $244 + 19 rush shipping. Do yourself a favor and search around. Universities have the lowest prices in some cases if you are a student or faculty member.
So, my take is if you buy a MBPr, you really don't know what you will get or will end up having and you had better factor applecare in to the actual purchase price of the product (not as a luxury).
Good night and good luck:)