I didn't experience any motion sickness or nausea at all when I was using it but it was only a short demo. Different people seem more susceptible to it and some games are better than others at preventing it.
My mum gets sick and headaches from watching 3D films so she'd probably suffer using one of these.
For me it's falling (in games) that gets me. I secretly believe that games like Assassins Creed and Crackdown were specifically designed to entice me with game play and then make me vomit.
My mate has Rift adn I spent a few hours on that a few weeks ago. Some of the games are no more than tech demo's (like the Vive) but I did enjoy playing game with it on, much better than the dev verison I had at the beggining of this year. If you get a chance to play on the rift make sure you have a go with BlazeRush. Top down game like micro machines, bloody awesome!
One of my team has the Vive so hoping to go around his soon and have a blast.
I cancelled my rift pre-order due to lack of funds, sort of regret it now.
Got a Samsung Gear VR on Wednesday. My mother in law had it free with her new phone and gave it to me :)
Much better than Cardboard. The extra sensors in the headset make a big difference and it's far less jumpy. My daughter loves it and keeps pinching my phone off me to use it.
Not much yet. A min cart/rollercoaster thing. Made me feel a little queezy but my 6 year old loves it.
Face your Fears was creepy. Sitting in bed with my headset on and also sitting in a bed in the VR world. A ghostly boy with bright red eyes moving around the room, disappearing and reappearing from the bathroom or air vent. Then suddenly jumps up from the bottom of the bed. Actually a bit scary, especially as I was in bed at the time :)