After reading the rest of the responses, here's a tip: just go with it. The seats feel really sturdy but it seems like some people felt uncomfortable in them....just remember that part of the mechanics of the ride include tilting the seats back so you physically can't fall forward.
My advice is just to be excited about it. I am such a wimp about rides (Test Track is the most intense ride I'll do in all of WDW. No ToT, RnRC, SM, etc...not for me) but Soarin' is my absolute favorite. It is SO much fun.
If you can, though, request to be in the third row because in the third row you're below the other two rows so you're only about 10-15 feet off the ground instead of like 30-40.