I am in exactly the same boat. I received my iPhone 5 on 9/28 as well and noticed a yellow tint immediately compared to my 4S. I gave it a couple days to see if it would improve over the weekend, but could not stand it anymore so I went to the Apple store yesterday.
It took a while for the Apple Genius to see the yellow tint, I am not sure if theyre pretending not to see it or what, but eventually the Genius had another Genius to come offer an opinion and eventually saw the yellow tint and offered me a replacement.
The replacement came out of a white box and I asked if they dont mind me activating it to see if the yellow screen persists. What a surprise, the screen was yellow tinted as well. At this point the Genius was confused as to why all the ones in the Apple store were fine but these ones are yellow tinted, so they asked me to come back another day to see if the issue has improved. As I am almost an hour away from the Apple store, I asked the manager to try one more time. And what do you know, this new one is even worse tinted than the first replacement. At this point I am so disappointed, the Genius goes on to tell me that they wont open anymore boxes because all of the new ones will be like this, apparently he says that the ones in the Apple store are on 24/7 so the screen has a chance to burn in or cure the glue. He then told me to give it a week, leaving it on maximum brightness on a white background overnight to see if it gets better.
I am quite disappointed that my whites look yellowish, my blue looks purpleish and my greens look lime neon greenish (ugh).
Will update in a couple days to see if it has improved.