Providing 90Hz / FPS for the 8K-X is a nice feature.
But let’s don’t forget, it always depends on the game you play:
Lucky Tales, Beat Saber, and probably a lot of other low-to-medium-graphic titles I don’t even know, might work well with 90 Hz in the 8K-X. And as those games don’t provide superior AAA-graphics, not as detailed textures, etc., of course I might not loose to much image quality when turning down some settings in order to achieve those 90 Hz / FPS stable 
On the other hand, once again:
If playing only low-to-medium-graphic games and/or turning down details, why should I invest in an expensive HMD such as the 8K-X is…? 
A 5K+ / 8K+ already would do fine 
Why did I upgrade from my backed 5K+ to the 8K-X ?
=> Because I play high-detail games and simulations, and although the 5K+ with 140% SS already was a very nice HMD, its image still remained a little bit blurry, and there as a little SDE. Just a little, hardly noticeable. But there was.
When I first tried my truck sim’s, Dirt Rally 2.0 or Elite Dangerous in the 8K-X, everything was so much sharper and crispier.
Nonetheless
… even the 8K-X still has a lot of room for details! Or better said: The 8K-X finally reveals, that
- 1k and 2k textures and sometimes even 4k textures still aren’t detailed and sharp enough when having the image right direct before the eyes.
- Same for shadows: When playing isometric games on the monitor or fast First-Person-Shooters on 32" in a distance of 80-100cm, I certainly can turn down shadows by 25 or 50%. On the one side, I am note close enough to notice the last lack of sharpness of the shadow edges; second, I am not as focused on such details as I am in VR. But when playing real world simulations in VR, and the shadows look blocky and weird, I will notice this instantly.
- As soon as lowering the in-game resolution or SS by more than 10%, the image tends to get noticeably blurry again.
- Even the two 4K-panels of the 8K-X itself aren’t the end of the line
I personally expect something between 6K and 8K-panels to be the minimum in order to not notice any blurriness and SDE any more.
But:
The other hardware - CPU’s and GPU’s - will have to grow with that, too, and so will have all the games: As long as the majority of the gamers are playing on 144Hz+ 28-32"-monitors, the resolution of textures probably will not improve as much as needed especially for VR.
So, from my personal point of view, we can look at that topic from all different sides:
But we still haven’t got the performance needed for really sharp, crispy, high-detailed VR-gaming with 75 Hz / FPS already besides VR casual games. Which of course is legitime for everybody playing those games and having fun with them, no doubt about that
But there are also VR gamers out there such as me or Timo and probably many others, which don’t see as much room for turning down graphics and details and optimizing FPS this way than the aforementioned ones. Just despite all of Pimax’ display improvements over its competitors 
, we still aren’t there where we’d like to be, if we just had a wish to come true 
So, for some, having 90 Hz now in the 8K-X is a welcome benefit.
For others, such as me, none at all 