All of the 15" rMBP's at my local Apple store had much better uniformity than my display. I know that the stores often hand-pick the best looking units for display, but this should at least confirm that good displays definitely exist.
I had to return mine for an unrelated (and very rare) dead USB port, but opted not to take a replacement immediately. I'm going to wait a bit and see how it turns out for those who have already gone for a replacement.
Interestingly, in line with Anandtech's review of the iPad Air all of the new iPads had much less yellow-looking screens even when compared to the very good looking MBP screens in the store. Their review showed that the iPad Air was actually on the cool side (>7000K) and I'd have to guess Apple has decided to lean that way a bit from now on due to the complaints of yellow screens. My iP5s roughly matched the iPad Air screens.
Samsung was known to be brighter in 2012 as well (if you put the LG on max brightness, Samsung just had one more bar to go [in theory]).
It wouldn't bother many people, since only few work on max brightness.
I wasn't complaining, it just is part of my theory on the cooler LG vs wamer Samsung panels; if the machines with LG panels are being calibrated after production to a cooler temperature that would slightly reduce their brightness. The Samsung panels, being left at their native slightly warmer temperature would be slightly brighter as well. This would suggest no major physical variance between panels, so calibrating a warmer Samsung to match a cooler LG would produce basically identical results. Again, just a theory.
Obviously uneven white temperature on the panel is another issue entirely, but you can get that from any manufacturer. That's just a matter of slipping past QC (or tolerances in panel temperature being too high to increase margins).
At this point I'd probably pay an extra 100 pounds just to get a good screen and to stop having to deal with this. LOL
I was tempted to see if they'd sell me one of those nice crisp-looking display models since I know they've only been out on the table for just over a week.