I received a week 47 iPad air 32gb/data directly from the factory in China. I also bought one in London a month ago which I returned because of the left side yellow screen issue. The new one had the same issue, maybe to a lesser degree though. I tried leaving it on overnight with a white photo to see if it made a difference but it didn't. I used it for a few days to see if I could get used to it, but then decided that even if I could get used to it, I don't really want to. Not for the price I paid. This is not a cheap item and I expect better.
I love it and want it, but not if the screen isn't evenly illuminated and evenly coloured corner to corner. I'm fine with a slightly warmer calibration too, but what I'm not fine with is the variation across the screen.
Anyway, just to add my experience to everyone else's. Might try again in a few weeks, but might just stay with my old iPad mini for now.
good luck to those who are still waiting for theirs to arrive. I did see one on display that seemed to have a perfect edge-to-edge white, even screen, but who knows if it was just the lighting in the store. The odds don't seem good.
It's vey hard to judge screen quality in the Apple store itself and on the display units, which are always cranked up to 100% brightness.