Yes, I've demoed this type of locomotion with a Vive. Teleportation is the de facto method, and causes no sickness. Try this in games like The Gallery, Budget Cuts, etc.

Yep, Vive devs all agree that 1:1 motion solves nausea, that's why it is a main Vive's feature. I think, I've heard it in the round table video on valve's youtube channel.

I watched half a dozen vive videos and I've never seen anyone complain about nausea. In my opinion the biggest obstacle is the lack of games or at the very least a killer app that justifies the pricetag.