I had the chance to "experience" Mission Space. Generally I don't generally have a problem with dizzyness like in the Teacups, and I really enjoy the simulators like Star Tours.
For me, MS was completely different from either of those rides. I did get an uncomfortable feeling being caged in to my seat, then having the door closed on our cabin. A person with even mild claustrophobia could have a hard time with that.
MS did not give me any spinning sensation at all because there is no visual perspective of spinning. You really feel like you are being thrust forward like in a rocket. The sensation of G-forces pulling on my face, arms, and chest remained with me the rest of the day. The ride doesn't pitch around like Star Tours. I enjoyed the ride, but didn't come away with the "let's get back in line" excitement of some of the other rides.