Nausea inducing incongruous locomotion is of course an absolute fail. But that is not a problem unique to VR, and for the most part you know it going in if you

Nausea inducing incongruous locomotion is of course an absolute fail. But that is not a problem unique to VR, and for the most part you know it going in if you're likely to get motion sickness. The actual issues with VR of eye fatigue are more subtle, and often hard for users to identify. They simply get an increasingly negative attitude towards the experience over time, and over repeated use. This is why an entire industry can spin up and have what seems like a great product, but have an odd lack of audience. The exact same thing happened with stereo in movies. The technology existed for a long time, but lost favor because it was a subtly unpleasant experience. Avatar and the modern resurgence of stereo has been more successful because of the decision to always converge the subject. Even now many supposedly expert "stereographers" try to emphasis the "stereo" effect by pushing the subject into a different depth from the screen by not converging on the subject. Watch a stereo version of Avatar without 3d glasses. You'll find that 95% of the film is completely watchable without glasses because the subject is always converged, or the shot isn't even stereo.