Vestibular mismatch remains an issue, but for seated sims there are hydraulics, for walking around sims - there is no mismatch. There's a crazy amount of experimentation going on right now with locomotion systems, such as some that involve you walking across your space, turning 180, and keeping the world fixed in your view, but with visible dust in the virtual air that becomes the main thing you notice, not the faded out world, and on you go.
For running/terrain, we just need backpack pcs and larger tracked areas. I already know of a startup looking to breathe new life into old indoor laser tag installations.
As to his anecdote - I stuck dozens of people in my dk2 and many were nauseous, myself included. On the vive - nobody - a d I've let far more people try it as a result of the overwhelmingly positive reaction - I had to pry my sixty something mother out of it.
Re: post simulation - that I concur is a problematic one. I can see very bad shit happening and it being ostensibly due to post-simulation experience distortion. I can vouch that it's very real - but that you do find your legs. After my first few sessions in the vive (never had with dk2, not immersive enough), I'd come out seeing things as weirdly unreal, too flat, and generally felt a bit "spaced". I don't get that any more - and my exposure hasn't been that heavy - maybe 50 hours over the last three weeks or so.