It appears that IR is a very old story on iPads... So nothing to be surprised about...
See:
[iPad] iPad 4 image retention - MacRumors Forums
From what I've read, it's seems that the iPad rMini Cellular is more concerned by the image retention phenomenon...
It could be very interesting to carry a poll with 4 choices:
- rMini Wifi only with IR
- rMini Wifi only without IR
- rMini Wifi+Cellular with IR
- rMini Wifi+Cellular without IR
So that people would like to exchange will be aware of their chance to have a screen without IR dependind upon their iPad model.
I bet that 75-80% of Cellular are affected...
Mine was manufactured week 51.
Btw, I confirm the retention is only noticeable when switching to a specific range of greyish solid background.
Grey backgrounds somewhat lighter or darker that the one used in the test show no IR.
And no IR at all on pure white, black, blue, red, green, etc...
After some hours of use, I can say the IR is nearly not noticeable during normal use, except if you search or provoke it.
Btw, far less annoying that uneven colors/brightness or dead pixels...
I also tested 4 others iPad (one 2, one 3 and two Mini not Retina) and all showed some IR, except the 3...
Given all this, I consider IR in the rMini is not a fault, but rather a technical lilmit of one of the new screen type used by Apple... Like color/brightness uniformity, backlighting bleeding are on other types...
Ironically, screens showing IR seems very good at color/brightness uniformity and backlighbleeding... At least it's the case of mine... and no dead pixel (finger crossed) ;-)