I've had the 52" 850 for almost a week now. There is no halo effect, which is why I returned my 750. The tv itself pretty much like the 750, but the bezel that surrounds the screen is not quite as big ~ did I say there was no halo effect!!! I just couldn't live with that...
Anyway, best looking tv on the market, as far as I'm concerned. Even the stand is glass, with the touch of color filling up all but the outer 1/2" or so. Very cool looking. I thought that I might like the 860 with the dark blue toc, but I think the red is better. It isn't as bright as the 650, again, more like the 750, because it is very subtle.
Picture is fantastic, and seems to handle sd channels very well. I had a problem with the amp with the 650 and the 750, and I'm not sure if they've updated their amp processing, but it seems to be smoother to me. The version and all other info are way different form software upgrade - info - than it was on the 650 / 750.
The only issue I have is with the flashlighting in the upper right hand corner. It isn't super bright, but my old tricks of energy saving / brightness / backlight adjusting doesn't do much to reduce it. You can tell these features work when you are watching a program, but with no signal, and the tv on, they don't seem to do too much as far as darkening the brightness. I'm thinking it could be because the tv is so thin, and the backlight is that much closer to the screen. I don't know. It does seem to even out a bit after the set has been on for a while though, but it's still visible.
The remote is upgraded as well. The 650 / 750 remotes were not programmable. The 850 is. The wheel is much more responsive, too. The menu comes up in a dark red color that equals the toc, and is pretty cool. I'm not much on dlna, but they have upgraded that as well. It includes the content of the 750, which I don't have much use for, but the pictures are stunning, just as they were on the 750.
I couldn't believe that they would let the 750 leave production with that design flaw of the halo effect. I really tried, but couldn't deal with it. Not for the money. I bought the 850 hoping that this issue would be fixed, and was so relieved that it was.
The 850, to me, is what the 750 should have been in the first place. Very cool.