I've heard people say that it's basically the story of Pocahontas but then in a different dimension.
You can see it like that but I would say that the story is not the most important thing here ... but it is good enough not to prevent you from enjoying what you see. And what you see -in 3D of course, that is what makes it really extraordinary- is, as Nicky confirmed, stunning. I could have done without the final "starship troopers style" battle too but I guess it would have reduced the spectrum of potential costumers.
Anyway, go and see it : it's a safe pick. And if you don't like it, I pay you the ticket back, promised