Q: Uneven backlight is "normal" on retina MacBook Pro?

I bought my 13'' Haswell retina MacBook Pro days ago, I've experienced the unresponsive trackpad issue and I'm happy to see it's already resolved. But now I've encountered a new issue, and it's about the display.

As the picture above shows, in low ambient lightning coditons, I can clearly see the brightness is uneven, the top left corner and the left bottom of the screen is brighter. The center of the screen seems brighter, too. But please ignore it because I suppose it's because of my poor phone camera quality, I don't see any significant brightness with my eyes.

I was considering replace it at first, but later I called Apple, the advisor told me it's "normal"!!! Actually, he said according to my description, my symptom is not very profound, of course I can get a replacement if I insist, but he really can't promise I'll get a better one since it's a normal issue on IPS displays...

To my knowledge, among all the Macs, only iMac and retina Macbook Pros use the IPS technology. I agree that my sympton is not that profound. The first time I noticed it is when I try to watch a movie in a dark night. In normal use, I can't say I have much bother. Except when I let the browser enter the full screen mode, since most sites use a white background, then I can see a small area of the left bottom of the screen is a little whiter, which is not profound but kind of distracting though.

I've asked one friend of mine who used the 2012 rMBP and he said he have the same condition too... So now I really wonder whether it's a common issue as the advisor said. Please download this full black image, open it and go to the full screen (or presentation) mode. Turn off your light and increase the brightness of your screen if it's set too low. Then check whether you have the same issue with me. Thanks a lot!