My first and only moment came a couple weeks ago while descending a very long hill.
The speed didn't phase me as I just let my legs go 'gumby'.
What got me was the rather large "ramp", for lack of a better term, about 3/4 the way down that was formed by a buckle in the road.
By the time i noticed the buckle I had no time to decelerate and found myself airborn for what felt like several seconds.
With a frewheel this would not have been an issue but there is something unnerving about flying through the air with your legs spinning out of control. For starters unless you are spinning in a balanced fashion the subtle torque differences actually cause the bike to tilt (think gyroscope) while in mid-air.
I hit the ground at an angle with a small chirp of the rear tire and managed to regain composure without messing my pants.
I held the front brake as hard as possible the rest of the way down and managed to stop for the intersection at the bottom (50 meters).
Once the ticker migrated out of my throat I actually considered trying it again.