I've gotten sick from the teacups (not horribly, not enough to go back to the room).
I did M:S twice this week. The first time, I was absolutely fine, no problem whatsoever. Yesterday, it made me sick the rest of the day (again, not enough to stop touring) and gave me a slight headache. Both times I looked straight ahead, yadda, yadda, yadda.
I would still suggest doing it once! It's a fabulous ride! Maybe make sure you're feeling OK going into it. I was starting to feel a little icky, so maybe it had nothing to do with M:S.