These are literally tiny LEDs - not OLEDs - with three colours per pixel. Which means that you get a very detailed, bright picture with a huge contrast ratio (and hence dynamic range - that's what you need for HDR).
It looks amazing. Even more so when you realise that it's made from small individual tiles that slot together invisibly. The edges of the tiles fit in between the regular pixel spacing so you can't see them.
You can build any size you like but the pixel pitch of the tiles is fixed, so if you want a higher resolution you have to add more tiles for a bigger screen.
At the moment, the technology is expensive. But that's likely to change as manufacturing costs fall. There's something that's definitely likely to make that happen: with any all in one high resolution screen, there's the problem of yield. That's the ratio in manufacturing of good screens to screens that are imperfect, perhaps with non-functioning pixels. With a tiled display, the risk is mitigated because if a tile is faulty, it represents only a small fraction of the screen and is easy to replace.
Right now, a 75" wall has a resolution of 4K. Apparently the next version will have half the pixel pitch (the spacing of the pixels), giving a resolution of 8K in the same space - or a 4K screen in a quarter of the space.
It's hard to overstate how important this technology will be in the future. As screens get bigger, they're more cumbersome and harder to install. With tiles, you can get literally any size of screen in through the door.
What's really significant here is the arrival of two relatively new technologies: Micro LEDs and tiles.
To be honest, when I saw this working for the first time, I was surprised at how slick the technology already is. It's several years ahead of where I expected it to be when I first heard about it. And the rate of progress is incredible: apparently it took Samsung only 4 years to get this far. So four years from now, who knows where we'll be?
I saw Samsung's Wall at Samsung KX, which is a spectacular purpose built experience centre near King's Cross station. It's completely free and has Samsung's latest technology on view. If you're in the area, it's well worth a visit.