Pros: Visually stunning. Brilliant use of lack of dialogue. Great character design. Brilliant animation. Full of beautiful moments. Marvelous score. Great end-credits sequence.
Cons: Loses some of its charm once humans enter the equation. What dialogue there is is rather blunt and preachy. Political ends are admirable but portrayed less than subtly. Would have worked better as a "silent" film - without any human dialogue at all.