"Despite the glowing positive reviews..." Crazy talk from the Tech Bologosphere : Controlling Oculus Rift’s Motion Sickness Side Effect, in other words Have it Professionally Fitted with the Most Precise Tolerances by an Oculus Fitting Expert and You Will Still Probably Get Sick

Despite all the glowing positive reviews about the products being next to perfect for virtual reality experiences, the developers have been receiving a growing list of complaints. There are certain side effects of using the head mounted display which could turn serious if not attended to properly. Most gamers have listed some common unpleasant features after using the Oculus Rift headset; some of which are: nausea, dizziness, headaches, sweating, shaking, etc. If players have been using the headset for a longer than optimal period of time, they may even start vomiting. All these can be grouped under the umbrella term ‘motion sickness’.

http://www.virtualrealitytimes.com/2014/12/22/controlling-oculus-rifts-motion-sickness-side-effect/