I have to say, that I am not someone is is frightened by heights. I climb 10 foot tall ladders at work without a though. But Soarin scares the bejeezus out of me! You can tell you are high up, don't let anyone fool you. Add to that the fact that the ride vehicle dips and sways with the movie, and that you can feel your feet swing, and you have one realistic ride. It does feel as if you are flying!
I've been on Soarin a few times, and actually rode with my eyes closed the last 2 times. I think I will be passing on it from now on.
Still, if you want to try it, I do think you need to ask for the back row. It is the lowest to the ground. Just don't look down.