Is everyone here reporting the issues they are seeing to Apple Support? I ask because I am seeing this as well, and the Support person I spoke with said he hadn't heard about this issue (which of course could just be the company line).
What I'm seeing is that the top 1/4 inch or so of my iPhone 6's screen (near the receiver) looks as if it has a slight shadow-like discoloration that does not appear on the rest of the screen. It is difficult to see the discoloration unless that part of the screen is completely white, but, when it is, that area looks a bit darker and yellowed, similar to how a weathered piece of paper might look. It's most noticeable when the ambient light is low, but is just as noticeable regardless of screen brightness. It's also more apparent when the screen is in landscape mode, likely because that area is then most likely white and my eyes keep returning to it as I read.
I'm not sure what to do about this issue. I'm thinking a good next step could be to take it in and have someone at the Genius Bar just take a look to see what they think, but even though this issue is painfully obvious to me, I couldn't get my girlfriend to see it regardless of how hard I tried. So, I'm not confident I will even get them to see it. I'm also not too crazy about going through the whole rigmarole of exchanging phones if they are likely to have the same problem (and possibly be worse), and I'm also not too crazy about potentially getting a refurb, as even though I'm past 14 days the phone isn't even a month old.
I have a feeling I might end up just living with it, which kind of ***** because I otherwise really like this phone (my first iPhone) and the screens of my last two phones - Nokias - were perfect.