I've ridden 269 roller-coasters with no problems, and yet the original (now "orange") spinning version made me pretty dizzy and lightheaded on the 2 or 3 times I rode it (before they invented the "green" version). Like the previous poster said, it gave me a headache as well on at least two seperate occasions. I can't stand Gravitron rides at a fair, and strongly dislike "positive g's", and MS gave me a similar feeling as the spinning, positive g-heavy Gravitrons, so I eventually decided I would just skip Mission Space.
Once they added the "green" version, I was able to begin riding it again with no problems! I can enjoy the story and every other aspect of the simulation without the annoying spinning or positive g's!
PS. One of my pet peeves about the original version of MS, as an "airtime addict", is that while the positive g's of being pressed into your seat are painfully authentic, the so-called "weightlessness" on the ride is really lame! For TRUE negative g's and weightlessness, you would float above your seat! But all they do on MS is stop the spinning and expect that this sudden lack of positive g force will give you that "floating" airtime feeling. Having experienced REAL airtime on numorous other rides, this doesn't come close! (same for Cyberspace Mountain at Disney Quest, which also disapointed me). So with no payoff of REAL airtime, there is no point in me riding the "orange" version! I just go with the "green" version and enjoy the story!