The CHG90 has a very weird 3,840 x 1,080 resolution (a 32:9 aspect ratio),144 Hz refresh, AMD FreeSync support, deep curvature and a $1,300 price tag, so it's not for everyone. It's built mainly to replace multi-monitor setups so that you can, say, game on one half and stream on the other. As a single screen, it could give you more visibility and flexibility with controls, but does not, obviously, deliver full 4K resolution.
It's interesting that a gaming monitor is first to receive the VESA DisplayHDR certification, as there are plenty of professional graphics monitors designed for maximum color accuracy and contrast. However, many of those use IPS panels that lack brightness and likely wouldn't meet the 600/350 cd/m2 threshold. Samsung has mostly used its QLED tech for 4K TVs, and while the blacks aren't as good as on OLED displays, they're definitely bright.
On the color side, VESA says that monitors must display a billion colors (10 bits), but 8-bit panels with 2 bits of "dithering" to simulate 10 bits also qualify. Very few monitors have true 10-bit panels, but most of Samsung's QLED TVs do (Samsung's specs for the CHG90 don't say).
VESA promised to announce multiple DisplayHDR certified monitors on or before CES 2018, so you can expect to see others soon. It will be interesting to see which is the first to conform to DisplayHDR 1000, which is much more demanding for brightness and black levels (contrast). If consumers start pushing manufacturers to meet those specs, it will be a big plus for both gamers and streamers.