I hate to tell you, but these are revision A's. This is the FIRST 21.5 inch iMac and the FIRST 27 inch iMac, with all new architecture inside. If the screen sizes were still 20 and 24 inches, you would be right. But as it stands, these are revision A's and do suffer the dreaded revision A syndrome that has been an all too common occurence with Apple over the years.
Mine doesn't suffer from it. It's absolutely perfect. White screen and grey screen from top to bottom with no yellow, flickering, noisy HD, crashes or anything of the sort.
It's a beautiful computer, that EXCEEDS my expectations.