Soarin' can't even be compared with Star Tours. . . it is difficult to explain, but the illusion on soarin' is just fantastic. I also wouldn't classify it as a thrill ride, and it is much less intense than Star Tours or Body Wars. If you are afraid of heights, get the back row, it doesn't go as high. I have also heard that if you have a tendancy for motion sickness, you should sit on the outside so you can look at the wall and establish some stability.
It really is a MUST do for my family. . . I was sitting next to my Dad the first time we went on and he was a little aprehensive because of a bad experience with a motion simulator in Vegas, but the second Soarin' started, he said "We have to do this again!!" And we did. . . again and again (it was Feb, so the lines weren't bad and we used FP some as well).