Do you know this for sure? It's the black viewing angles that are the biggest change with the 2012 iMacs, so I find it hard to believe that these are the same panels. Maybe it's the fused displays causing the issue, but something has definitely changed with the 2012 iMacs. I don't have any backlight bleed - just the viewing-angle anomalies that everyone else has.
Interesting.. I haven't spent much time with the prior generation imac, but it does seem like the viewing angle anomaly seems to be the norm here. It's a bit disappointing. I have one bad area of backlight bleeding on my screen that doesn't go away at any angle. The corners, however, do exhibit viewing angle issues, especially at close distances. But they definitely go away as you look at the corners dead on.