I got one for my dad. It was the 4K Express, and I set it up with my own credit card but passcode protected for any purchases. Seems easy enough to use, but the quality wasn't that great on a 4K TV. I don't think it's the internet connection, although I could test it next time I visit. They've got Comcast and don't stress it with much else. It would always start off slow and then just getting better, but still nothing like I'd expect with 4K. I set it up for auto resolution detect and then 4K, but it still looked less than ideal. I'm thinking of just taking it home and seeing if it's the TV or the internet connection.
But yesterday he was able to watch the ESPN "Above the Rim" broadcast of the Heat-Celtics game, which was really bizarre because it was a single camera mounted behind the backboard. Nothing quite by being blocked by the edge of the backboard. Most of these were mounted on top of the shot clock where they'd switch, or even sometimes just go with a side camera but no announcers.