I'm a bit late on the Up review, and to be totally honest, if you are wondering why you should even watch the most recent Pixar film, I judge you for not believing in the magic of Pixar. Their ability to tell great stories with morals for all ages is astounding, and I am reminded of a Wondercon panel I went to this year about why they took so long to release Toy Story 3 and the man replied something along the lines of, "When we decide to make a movie, we wait for the perfect story, and we know that if we don't make this movie, it would be a shame".
[FYI: Possible Spoilers Ahead]
That's exactly how I felt when I finished watching Up. If they did not write, create, direct, and produce this film, I feel that the audience would have missed out on a truly special story. I emphasize audience and not children or youth because one of the unique aspects about Up is that it's a story for all ages. In fact, I would even argue it's targeted more toward the adult crowd. It tackles some extremely important issues about relationships (child rearing and infertility for one], and although they approach them in a kid friendly way, I for one was devastated when there wouldn't be a little Carl in this film.
But even though it had some deep and tragic moments, it's a Disney/Pixar film, which means there were more than enough laughs to make up for those misty-eyed moments.
I know the review is short, but I feel that the proof is in the pudding. 98% on Rotten tomatoes. #1 in the Box Office. The history of the Pixar name.
Stop reading. Just watch it. You know you want to.