I went into this movie with low expectations. I was expecting rushed-out holiday crap. Man, was it a surprise. As it turns out, this movie was really well done. The story was interesting and fresh. The comedy wasn't forced and the jokes were actually funny. All of the characters were interesting and well-developed. The actors were great. All of them. Even minor characters pulled off their rolls perfectly. And then there's the animation. The animation was amazing. Asides from the awesome scenery, we got so much emotion from the characters' faces and body language. Combined with the good acting, you almost felt like these were real people. I nearly started crying at the scene where Arthur is all depressed, thinking he's failed, it was that convincing.
All in all, I give this movie a 10/10. I saw nothing wrong. It's as fun for adults as it is for kids, and I really suggest you watch it.