We had planned on watching Shall We Dance, but had to settle on Polar Express because Shall We... was cancelled unexpectedly. Good thing, it turned out.
Polar Express is a delightful movie. Though it is primarily meant for children (we were feeling slightly out of place in the theatre, being surrounded by kids -- most of the other grownups were escorts for their children), the story is handled in a pretty mature way; there is not much of the usual wheee-we-are-all-happy-kids-watch-us-fart-around-with-nary-a-care nonsense.
The animation is quirky, though. The action sequences involving the train were very good, but the facial expressions of the children sometimes made them appear, well, retarded.
Obligatory favourite scene: ski-ride on top of the train with the ghost.