I can play AC all day long - no problems after a small initial acclimatization. No problems with any of the content designed for VR - except maybe Eve: Valkyrie if I do the barrel roll thing. But I tried Skyrim using VorpX and even though it works well and looks cool, I found the same as you - under a minute and I felt terrible. Tried a few times, and doesn't seem that I'll be able to do it.
May have to do with VorpX / framerates / FOV. I used to think if I could just get games to render in VR it'd be no problem, I guess there is a lot more to making it comfortable than I gave it credit for.