Within reason, nausea is something you'll experience based on design of the software, not the hardware. Some Rift games will be absolutely fine, others will turn your stomach. Same for Vive and PSVR.
I managed to try the Rift and Gear VR at a little expo in Brighton. The Gear was interesting but it simply isn't designed for more than 10-15 minutes' use - the lenses they use to curve the images render most text seriously blurry. The main interest with it is that it's more readily available to non-game studios - the two things I saw were a Guardian feature about solitary confinement and a creepy live-action trailer for some dance theatre troupe. It's pretty much where you'll see a lot of people dip their toes in the water with creation of VR media.
The first Rift game I played was extremely fast (some Wipeout style game where you raced on the outside of a cylindrical track) and something about the head tracking was ever so slightly off - I felt a tiny bit queasy as a result. Someone else was over in the corner playing a combine harvester simulator. I know. But I do think VR has a big market in training - driving schools, race-driving schools, heavy machinery, bomb defusal etc.
The best thing I played by a long way was a game called
Private Eye VR on the Rift. Having a room space to roam around in, plus having in-game hands (everything else I played was either just the headset or an XBox pad) was a bloody revelation. Little things like rooting through drawers, finding a torch and then needing to find a battery to put into the torch, lining up wooden blocks to reveal clues, using a mop to knock things off a high shelf - I was 'present' from the moment I put the headset on and peered around and under the desk in front of me, but the real difference between VR and standard games is that interacting with the world is second nature.
This generation of VR might not be the one to do it. There will be countless developers who never really get it, who just try to make existing games in VR rather than really understand VR's potential. But over the next 5-10 years, as new things like more sophisticated hand controls or inner-ear fluid conduction give us more of a connection to the worlds people create, VR will genuinely dominate. I only hope Rockstar are looking at an LA Noire title, or that more is done along the lines of the Walking Dead / Game of Thrones titles. It'd blow standard films & games clean out of the water as an immersive experience.