I haven't tried VR so I can't really say much. However I believe optics are require to create a virtual image that is focussed away from the 2" that the screen really is. Our eyes cannot accomodate such a close object. Being near sighted I have increased accommodation for close objects without corrective lenses that is.
The size and position of the virtual image has to be correct for a 1080p image. Which most people will say is not closer than approximately twice the height of the screen. For 4k you can be much closer. And hence have a much wider field of view. I'm not afraid that 1080p will be too little for a first generation product. I might be wrong.
No doubt 150fps is going to extremely hard to accomplish and even though NVidia claims this new VR SLi tech they haven't shown this stuff to work properly without microstutter. I have almost no hope these people can get two GPUs to sync correctly enough for VR.
I'm seeing a lot of evidence suggesting the days of games not using more than 4 cores properly are over. Some recent benchmarks are showing 6 and 8 core CPUs coming out ahead for once. So it's going to take some high end hardware and some great coding to pull this off. I'd say still about 2 years away though. Can't even drive one 4k display properly today.
It's VR, you're not viewing a virtual screen. You're looking at things that feel like they're as far away as they would be in real life, not on a flat plane at a set distance. But you can still clearly see the grid of pixels right in front of your face. It's almost hilarious how that between the low pixel density and the warping, UIs and text need to feel like they're plastered on the side of 5 story building that you're standing in front of, and you need to whip your head around to read it all...because otherwise it's completely illegible. Trust me, the 1080p screen in the DK2 feels like you're playing in 240p....it's SO BLURRY. When they play the cutscenes in AI, there is a virtual screen and it's so huge you can only see like a quarter of the screen at once...any smaller/further and it'd feel super low resolution.