Chiming in, my
week 20 had a warm, dull display. I showed it to a
genius, who compared it to his week 25 phone. The difference was significant. He only had one eye and saw it immediately. A replacement was setup and I mentioned that I'd prefer a replacement from week 25.
The replacement screen's white point and vibrancy were excellent. Unfortunately, it was sullied by a centered cluster of (evil) hot pixels. So, it was replaced with a week 24 whose screen did not have the same pleasant white point, nor vibrancy, but it was an improvement. So, avoiding further annoying my one-eyed genius, I took it.
On the way out, I looked at all the display units and checked the serial numbers of each. I was surprised by the degree of variance among the units. For the most part, the higher week numbers had superior displays.
I wish I had that week 25, but at least this 24 is an improvement. So, I'm happy, sorta. :P