Pretty good pixar, one of the best animation that I ever seen in my life. Nature has never been so real! And that's a bit a problem, considering that all the characters even the human-pet, looks so animated. the contrast is quite shocking.
About the story, it's actually quite dark and deeply sad for 60% in the movie. Which is pretty too much in my taste when I want to watch a Pixar. In comparaison "UP" was sad for 20% in the movie (in the begining) and then moved on to a lighter but still a bit emotional without getting too much weight for the viewers.
Back to "The good dinosaur", the movie is beautiful as I said and I didn't understand the need to repeatedly (every 15 minutes) bring back deep a sad moments, until the very end of the movie.
I loved the references about the western movies and the amazing work on details, landscapes.