Heard about this game today on another site, and was talking about it at work with a coworker.
The PS3 version is definitely going to be the version to buy - it's hard to imagine Ghibli visuals looking as good on a small handheld screen.
STK tipped me off to this: track down Miyazaki's 7-volume manga-adaptation of Nausicaa that goes far and beyond the cartoon in every conceivable way. He wrote it over a long period of time (most of it was written after the movie came out, and many parts are different and much more deep and complex), and it will probably jump to the top of your list of his work --it did for me.
The comics are obviously better than the movie (which was good, I'm not trying to criticize it) but much like every Miyazaki story ever, the ending is rushed. I've always felt that the endings for his projects have been a let down.
For the Nausicaa comics I remember reading an interview where Miyazaki said he had to end it because of scheduling, so he did it as fast as he could, and I think it really shows.
It almost seems like the bulk of his energy goes into character, setting, and scenario creation, and the actual story arc plays second fiddle.
And in the situations where he adapts other people's stories (Kiki, Howl, Earthsea) he usually makes inexplicable plot changes for the worse.
So I'm looking forward to his "version" of "The Borrowers" with very mixed emotions.