Just going to address the screen issue directly since I don't have enough data to comment on other aspects of Apple's QC.
My rMBP did have a dead USB port, but I know that failures of that type do happen in any electronic device (and may occur after testing). No offense intended to anyone on this site, but I feel like the constant replacement for "creaking" falls into OCD territory and don't take it into consideration when thinking about Apple's overall quality.
I originally picked up a 13" Haswell rMBP, but I was so unhappy with the screen uniformity that I decided to just jump up to the 15" (assuming quality would be overall higher on the higher end device). Unfortunately it was about as bad. I don't have the appropriate equipment for measurements, but my white balance looked quite a bit like the map you posted (yellow towards the bottom and corners, white in the top middle).
I think the question to ask here beyond "has Apple let its QC for non-iDevice products slide" is: Can Apple even find anyone who can produce good quality "retina" MBP panels? LG's panels had ghosting issues, and clearly Samsung's have terrible white balance (the luminance chart is actually not terrible, but the white balance variations wouldn't fly on a review of a high end monitor/TV).
I'm left to wonder if there simply isn't a display manufacturer out there currently who can produce high quality panels at Apple's specs and cost requirements. Apple orders unusual resolutions (and ratios, which I really appreciate) and we're not talking about particularly high volume orders. They can't use volume to reduce costs (which they certainly can with the iDevices) nor are they buying the same panels as other manufacturers.
They could tell Samsung and LG "we won't buy your panels unless you improve quality," but at that point what's their option? IGZO panels from Sharp I suppose? Now that we've seen an IGZO iPad it's not hard to believe a major display upgrade is coming for the MBP next year, even if only in terms of the technology behind it (which is what I'd prefer to see instead of a resolution boost).
Basically I'm saying it's a tough situation and I'm not sure how much leverage Apple has in this case. Certainly not excusing them for the display quality issues (especially since the device is advertised on its supposedly amazing display quality), just not certain how they can fix it without increasing costs.
The uniformity issue is incredibly annoying. I don't think the issue is with LG or Foxconn though. If that is the best they can turn out at the required yields and they are the only options, Apple may have to consider what correction can be managed on their end. Since we're talking about higher priced items, it should be possible to do more than shove a panel in a box. They are basically oeming a panel, then turning out a finished product.
I should read the whole thread before I post because you basically said what I wanted to in a much simpler, more direct way.