Because the movie had a lot of ground to cover from the first book, there was not as much character development as I would have liked, but it was more than made up for by the excellent casting. So much was conveyed by a look, a stance, and the right people playing the characters. My whole family loved it.
This is a movie with something for everyone - we had two eight years olds, a ten year old and a teen with us and everyone loved it! The dogs were funny and cute and the really like dogs. Alpha's voice was very humorous. The animation was stupendous -- water, rocks, the shadowing and lighting on the balloons was so well thought out. The first part may have been hard for the littler ones to follow, but the essence of time passing and the sadness was certainly felt. Pixar has done it again!