Farah Mendlesohn has a terrific article in the March/April Horn Book called The Campaign for Shiny Futures. Oh, and look! You can read it. (Sheila, you want to read this.)
So many seriously thought-provoking things here that I don't know where to start. I will just say that I'm going to be thinking about didactic books quite differently from now on. At least, I will if they're didactic science fiction.