Here's my update. After shipping back two 50r550a TVs for excessive Dirty Screen Effect, I was offered a 55w802a for no extra charge. I just received it and I love it. There is no excessive DSE at all. For some reason, GTA V I could see the DSE the most on the 550a, must be the color pallet. Playing it now on the 802, I can see some light and dark streaks here and there, you know it's not perfect, but very hard to see, and I'm really looking for it.
There is also no excessive backlight bleed at all, compared to the 550a. Still have to consider room luminance and brightness settings, but when set correctly the blacks are great.
I liked the 550a picture overall, minus the DSE (especially) and flashlighting (just a little), but the 802a is absolutely stunning IMO. I even get to keep one 50" 550a, but I have no room for it, and I'd be embarrassed trying to sell it the DSE is so bad.
I would echo tgm1024's advice, don't tolerate poor quality TVs. Make sure you hound Sony until they make it right for you. A $900 TV isn't cheap, and you shouldn't have to expect excessive flaws.
And thanks to tgm1024 for starting and maintaining this thread, and for everyone's contribution, it's been a tremendous help through this whole inconvenient process.