I'm 49 and will ride most thrill rides. I especially love ToT. Soarin is different though. It's the closest I will ever come to understanding how a bird feels and seeing things as they do. Well, that sounds stupid.
Let me try again... it's hard to explain, but riding Soarin makes me feel free somehow. At 49 and with a lifetime's worth of responsibilities and baggage, that feeling is hard to come by. I've never ridden anything else like it.
Because Soarin is thrilling without being jarring
This is my theory: ALL adults love Soarin. My DM, who will not go on ANYTHING thrilling what so ever, ranging from EE to Goofy's Barnstormer! But we dragged her on Soarin, and, of course, she loved it! Even though she hates hights and fast motions, she was perfectly fine! I also told her (afterwards of course), that she was about 30 feet in the air! Who else here LOVES Soarin, but can't go on anything else?