My DH, Brother-in-law, DS7, DD15, DD11 and dear nephew(6) all rode on July 20th. DH and the girls/boys were fine- my DBIL was quite ill. Everyone but DBIL went on mutiple times over the course of the week. The boys/girls are too "naive" to close eyes/turn heads; my DH knows enough about visual perception that he heeded directions. DBIL would'nt try it twice! My DH did say that there was incredible chest pressure/compression, much different than any coaster sensation. I have an inner ear problem (horrible virus of middle ear nerve that is taking FOREVER to heal), so no ride for me; besides, I'm a wimp).
My DH's impression: if you are prone to motion sickness AT ALL and think you might be likely to close eyes/move head- stay away. If you can control the motion sickness and your head/eyes, its fine. My coaster-fanatic children rate it as not as "adrenalin-junkie"-like as a coaster, but way cool!
Guess the youngest DD5 and I will stick to IASW!