From what I've read, there's a lot of "stuff" to do in the capsule as you're riding...pushing buttons, flipping switches, etc. For those of you that got sick, are you doing all those things? Or are you sitting back and staring at the screen?
My experience with motion rides is that I do a LOT better if I can find a focal point on the screen that, relative to me (and the other things on the screen) is fairly stationary. That, or if I can anticipate the direction of motion and look as it's changing in that direction, I do OK. Not great, but OK.
Think about it this way...some people get sick RIDING in a car, but not driving. Why? Because they are in control of the car, and they know which direction the car is (and will soon be) moving. Even through a turn, 'cause your vision pans right anticipating the direction you're steering the car. You're in control of the car, and you anticipate that movement, and you (and your brain and ear) have no surprises.
In a motion simulator, if you're looking down while moving, participating in the ride experience, and yet still moving, your brain gets messed up because the stuff you're seeing is NOT moving, yet your ear tells a different story.