I can confirm that I have this on my new 13" MacBook Air (Early 2014). At first I was considering bringing it back to the store for a change, but after I spent a couple of hours reading various threads discussing this issue, I decided to keep it and go along with it. (It seems that all Airs have this issue, only the degree of a shadow varies).
The main reason for keeping current laptop is that I'm afraid to get a computer with bigger problems. I've already had one change (just another day after buying), because of loose trackpad, that was making noises just from touching its surface.
I'm a little bit disappointed, because I had absolutely no problems with apple products before, all of them (black macbook, iphone 3, iphone 4, ipad 3) were perfect just out of the box.
Still not sure If I my decision is right. Maybe I should still try to change it at the store. Maybe some of newly produced Airs do not have this problem?