My review will be very short in my writing, rather start by reading Matthew Sorento's review here: http://www.filmthreat.com/index.php?section=reviews&Id=11758
I agree with the points that Matthew makes and it really does hit the nail on the head that Up seems to take a great concept and throw it into a blender with a bunch of other random ideas. Three questions that arose in my head over the course of the movie.
-Why do the dogs always yell squirrel when they've been raised in a jungle where I doubt squirrels exist?
-Why is a man who is at least 25 years older than the main character at least as spry?
-Why do we see the main characters trudging through jungle when every time we see their environment from afar they are at the top of a huge rocky ridge?
I thought the movie failed to really explore its exploration concept further and instead went on a more typical romp for the second half, however the mood of the first half was strong enough to carry through the characters for most of the movie and I did indeed come out of the movie wanting to accomplish something with my life. The movie was very strong emotionally, and hopefully they can tie that up next time with just as cohesive a narrative.