Well I'm one of those few madmen that acutally liked Waterworld, not totally sure why. And yes, I'm the sort that likes 'after the bomb' games/movies/whatnot. I miss GammaWorld...
I can understand the apeal of the Flying Islands though. It's pointed out in the Core Rule Books that the 'point' to Dungeons as the mainstay of Adventuring, at least in part, has to do with them being self-contained little worlds. You enter and you're in 'the dungeon', you leave and it's over till you go back in, very cut and dried. This appeals to many, myself included. Think of the "Flying Islands" as a really big dungeon, only over-land and not just underground (which can wear a bit thin I'll agree).
Maybe that's a part of why Water Worlds have appeal as well. Your ship or Island is the isolated 'dungeon' you're dealing with, yet you can take it with you around the world. *shrug*
Hatchling Dragon