I stopped in the "dark living room" area of Best Buy today, looking to see if they had any 4K demo units set up. I've only seen them at BJ's before, and the one there was just playing a canned commercial loop from some unknown signal source.
The Best Buy guy offered to show me a 4k bluray disc demo. He took me over to an ugly looking curved shiny-glass screen model, a Samsung J9500 I believe. It looked 50 or 55 inches or so. Even the black screen as he popped the disc in was running ridiculously white hot brightness, it was practically light grey. I asked him about what they had it set at, he said their general policy is to keep at it factory default settings and just leave it on demo mode.
The demo disc was Life Of Pi. First I saw the 20th Century Fox logo, ridiculously orange, so the default colors were hot too. He jumped to the scene where the kid is swatting at the tiger on the boat with a pole. After a few seconds I asked if he could turn the motion smoothing off. He made a valiant effort to dive into the Expert settings, but when he tried to change it, the system was locked, hahahaha.
I gave it another 30 seconds, then thanked him and moved on. It was difficult to make any judgements on the quality of the 4k disc with such godawful settings on the TV. The motion smoothing was hitching too, so I think the movie wasn't playing in 24fps. The tiger looked sharp and vivid enough when he stopped for a second, but also noticably pixelly. That could be jacked up sharpness settings on the TV, so I couldn't make any judgement on resolution either.
So, if you are shopping for a 4K TV, making an informed purchase must be pretty diffcult. Even Best Buy employees are locked out of the picture settings, hahaha. Maybe a manager could override it if they were chill enough? Best Buy, BJ's, and Target are pretty much the only places to get a 4K TV out here in RI (the guys at Target are dickheads, I didn't try asking about settings there). Maybe if you are on the west coast, they'd be more accomodating at a place like Fry's or something?