Just got back from WDW on Saturday. I didn't think we would see the balloon but it was there. If it was open I would have done it, particularly since I figured they would charge $45 or so. $16 would be fine.
Lily and I did one of these in Paris with some friends. It was more expensive there, too! It was fun, though, so we'd probably do it.
We did see it in DTD last week, and even though it wasn't going up in the air it looked pretty cool. Lil noted that all of the characters on the balloon are ones that fly. Really cute!