I have written a review of this monitor before. Now quite a while later I've purchased another one to see if there's been any improvements since last time I owned a HG90.
I had issues with the backlighting in gaming mode + issues with the backlighting zones beforehand.
The difference between the previous monitor I had and the new one i recieved today is night and day, so much so that I doubt it's just firmware upgrades that are the difference. I recommend disabling the backlight zones in SDR as they still cause some funnies in certain games.
Other than that the monitor performs excellent. The insane blur that I experienced on the other monitor is nonexistent here, using the gaming mode is almost not really necessary. In gaming mode this monitor is also more than bright enough, almost a bit 2 brigth for how I generally keep my lights in my room. Haven't gotten to test the HDR much, but I assume it's pretty much the same as it has been. Pretty basic, not really well supported and windows HDR stuff = pretty basic and buggy. There are plenty reviews on youtube that test the HDR properly. I honestly don't find it necessary.
Picture quality is excellent, colors are vibrant and very nicely balanced, very little blur, overall very good quality overall. I'm not bothered by the 1080p resolution as I prefer framerate over pixel density. All in all I'm very happy with this monitor, again, so much so that I suspect the panel had more issues than just a few dead pixels on the previous one I owned.
I've tested LG's 35" ultrawide, Predator Z35/X34/X34P and AOC Agon 35". There's no comparison between the HG90 and the forementioned. If you really want a higher resolution I would go for the X34/X34P(they both have their pros and cons, most people seem to prefer the older X34 model).
All in all an excellent product and I kind of regret not testing another one of these when I returned the first one. I would still like to see more backlight zones and proper HDR10 support but I'm sure that's coming down the line, and with the pricing of the current HDR10 monitors I don't mind the HG90 at it's current price at all.