Long time lurker, first time poster...
I picked up the UN46D8000 at Fry's in Austin recently and am very pleased with the TV's performance. The quality of the picture is stunning and quite a bit nicer than the C650 set I had been watching. I haven't experienced any problems with banding or light bleeding.
One thing that has surprised me is the quality of the 3D on this television. Stunning. I didn't have any particular interest in 3d and had been very underwhelmed by my prior experiences with it on friends' TVs and in stores. I recently tried out the 3d on the 46D800 with some of the DirectTV 3d channels (3dnet mostly) and was very pleasantly surprised. Wow. I still haven't tried out any 3d bluray movies or games on the ps3 but am excited to do so now.
A few minor quibbles: the qwerty remote leaves a lot to be desired and I'm not especially impressed by any of the smart tv applications. As another member mentioned, the arrow keys on the remote have a tendency to skip a bit (ie, I press right once and it goes right twice.) Also, the button in the middle of the arrow keys on the qwerty side of the remote seems to be a track pad of sorts--you can use it to move a mouse cursor around while web browsing. But the web browsing experience (along with facebook, etc) is underwhelming. It feels sluggish and I'd rather just use my laptop. Also, after the youtube app updated it no longer accepts input via the qwerty side of the remote. Strange. I'm sure they'll fix it in an update.
The sound from the TV is adequate bordering on good. I tried the SurroundSound effect and it sounded nice on some programs and really poor with distortion on others. I'm sure most people will probably hook this set up to a nice stereo system.
Overall, I'm extremely happy with the TV and would easily recommend it to others.