So I've had a few days with the 82" now, and have replaced my HDMI cable with a new one. I was a dummy and actually had my Xbox 360 HDMI cable plugged into the TV. Don't believe it was a high speed HDMI cable, or could have been damaged over time, but after replacing I haven't seen the skipping issue like I was before.
Distance viewing wise, I'm around 16' and feel 82" is a great size for this distance. I was afraid it would be too small, and would be honest if I felt it was, but truly...at least for my preferences, it seems like it's perfect. Could go bigger (maybe in the future), could even go a little smaller to the 75" (but I wouldn't want to)...however there's no issue whatsoever viewing it as is. It's big enough that you have to noticeably move your eyes/head to see details doing from one side of the tv to the other.
4K streams look awesome, as one would expect. Fast moving scenes see a little bit of jitter and fragmenting when I'm right on top of the screen (< 8 feet), but viewing 12-16ft you can't really see it at all. I binged Season 2 of Stranger Things on Netflix and it was a pleasure to watch...crisp and clean. ST2 from what I understand is recorded with 4K cameras, so no upscaling. Other 4K sources I've seen may have been upscaled and resulted in that minor jitter/fragmenting.
HD cable TV channels look good but not great. Fast moving scenes show more noticeable jitter and fragmenting, but again at 12-16 ft, it's not a big deal. It only feels like a problem because of how good 4K looks in comparison. You start to nit pick the details.
Standard def cable TV channels as expected looks like crap. They're watchable, but not fun to watch.
Ultimately, 4K viewing will spoil your eyes. This is my first 4K TV and I'm crazy observant with details, so I notice the differences easily on things that others might not see or might not care about. And like most things, when you don't have something better to compare it next to (i.e. 4K vs 1080 vs Standard)...you notice far less and probably won't be bothered by it. However when you do have it to compare, it really makes you not want to watch anything but the best (cmon more 4K content, especially Sports streaming!!!).
I can say the TV display is beautiful with 4K, and because it can display it well, then the poor viewing issues are likely an indicator of the quality of the stream you are running. Things on a screen of this size are really magnified. Pixels aren't condensed and the lower quality streams tend to expand the pixels, blend colors and show aberrations that would be more difficult to see in smaller screens (think of how a non-high res photo looks on an iphone vs a 27" monitor). So it seems the only thing to do is enjoy the hell out of 4K and wait for the world to catch up with more content! The TV seems fully capable of accommodating it well and in the interim I'll have to avoid being nitpicky about the 720/1080 streams. Without question, for the pricepoint, this TV is excellent!