I remember how much talk of possible image retention issues there was when the display in the Retina iMac was found to be an LG. Now I find that my launch-day order Retina iMac is just barely starting to develop this. Not nearly as bad as it was on the mid 2012 rMBP I once had, but it is there nonetheless and I suspect it will get worse over time. Just a heads up to Retina iMac owners in case this becomes a widespread issue. It is worst in the upper right corner where this photo was taken.