The two main problems with VR not feeling quite right is the virtual world not reacting to focus and aperture changes in our eyes. The brain gets confused, and

The two main problems with VR not feeling quite right is the virtual world not reacting to focus and aperture changes in our eyes. The brain gets confused, and that creates this sense of confusion and that something is wrong. These can be solved some day though by following the eye's aperture and focus and adjusting the "world" with minimal latency.