Well my dark corners saga finally comes to and end
I called Sony Support and they walked me through resetting the TV (holding Up in the remote while pressing power on the set) followed by turning off the main power switch and unplugging the set for a min before turning it back on.
I followed the steps merely to humor the rep, but found that the shadows did get much better. After getting off the phone with the rep, I tried it again before going to work, this time leaving the set unplugged for about 9 hours while I was gone. When I turned the set back on, the corners were much, much better, but unfortunately still there. I'd say it was a 90% improvement.
I couldn't see them in normal programming or movies for the most part anymore, but every time I turned on the PS3 or played a game with light colors, I'd see them because of the mostly uniform background on the XMB.
I tried to not let it get to me, but I couldn't help it. And I didn't want to drop that kind of money on something that was going to annoy me until I got rid of it
Luckily I found a 55" locally at a nice discounted price so I picked that up and returned the 46". The 55" is PERFECT. Haven't seen any dead pixels or major clouding, but most of all the corners don't have shadows!
Since other people with 46" sets have confirmed they also have shadows, I think it's just an issue with that size. All the 55" sets I've seen (including the one I just bought) don't have the problem. Sony did offer to sent a repairman to fix the 46", but seeing as I was still within the return period, I decided to go that route instead.
Side note: Someone posted the dimensions of the 55" box as 53 1/2 X 33 1/2 X 8 1/2. It's actually 53 x 33 x 8 which just BARELY fit in the trunk of a 2010 Civic Sedan with the seats down. Guess no 60" for me without paying for delivery