Apple must be pleased! Also, good luck finding any 27" panel from any manufacturer that has even backlight when looking at a solid grey screen. It looks to me like you're looking for issues/attention.
Also, for the record, the underlying panel in the 2012 is the same 27" panel you got in every old 27" iMac, the ACD/TBD and most of Dell's 27" panels.
Well I had about the same issues and wasn't even looking for them on a gray screen. It happens during day to day use!
I like the products of apple and don't want to exchange anything. And that former iMacs don't have problems don't say anything even if that use the same panels.
Lets just face it there are a lot of problems with displays from apple at the moment/ recent pass.
I love apple love Mac OSX but saying that nothing is wrong is just ignorant.
Note: I don't say these problems are not existence at other company's displays.
I just wait for the next iMac speed bump upgrade and hope they will get rid of the display problems.