I got to try the Pimax 8K VR at GDC 2017.
Current Oculus Rift and Vive systems have about 100 degrees FOV (Field of View) and about 2k resolution (1k per eye). PiMax's 8K VR has 200 degress FOV and 8K resolution (4k per eye).
Field Of View
The 200 degree FOV does make an enormous difference. You no longer feel like you are wearing ski goggles. It feels like natural vision since your periphery is no longer blocked.
8K Resolution
The headset was running the 'Showdown' demo by Epic Games. Its an on-rails experience where you have soldiers firing bullets at a Robot in slow-mo Matrix style. The demo was using an NVidia GTX 1070 card.
8k resolution truly feels next-gen. There was zero screen door effect. Objects looked perfectly solid and you could see the details up close. There was no aliasing. Apart from the obvious graphical artwork of the world, there was nothing to indicate I was in a digital world. It felt like a real, solid world.
Ergonomics
The headset shown was a prototype which you had to hold with your hand in front of your eyes. There was no indication of how the final headset's ergonomics would look like.
Conclusion
Current VR systems are designed around the compute power of the NVidia 980 card. Pimax demonstrates what the NVidia 1080 card can do for VR.
Going back to Oculus Rift after trying the Pimax feels like wearing a last-gen headset. Like using the iPhone before its 'Retina' display. This demo proves that the tech currently does exist to support an 8k resolution VR experience. I am sure both Oculus and Vive teams know about this. The reason why neither of them mass produce it currently is due to the cost of the components involved and the need for consumers to yet again upgrade their graphics card to the latest NVidia offering.
However, using the PiMax gives you a sense of how all future VR systems will look like in a few years. It is a huge leap forward from systems of today.