I see the dark corner/edges to on my 55" on white/light backgrounds. I don't notice it very often though as most content either entertains me enough not to notice or isn't plain enough to enact the discoloration. I think it was mentioned previously in either this threat or the E-Series thread that it is an inherent issue with the panels used. I'm still very impressed with my 55". I was watching baseball on ROOT Sports last night. ROOT doesn't usually bring the best picture quality to the table, but it looked much better than I remember on the new TV. Then I switched to MLB Network and was really blown away with the representation of the MLB Tonight set pieces (lots of deep blacks, blues and reds). I did not notice the dark corners when viewing either of these shows.
I know the general consensus here is to forget the TV has built in speakers and use your sound system, but has anyone played around with the equalizer and found a setting they like more than others?