Up: The Non-Conceited Conceit

Just saw Up last night, and, I'm happy to report, it lived up to the hype. My roommate Jason commented before the showing that Pixar has been very good at making movies that are compelling to children and adults for the same reasons. I agree. Today's entry will be a short one. I just want to present Up as a counterpoint to Pan's Labyrinth in that it uses its conceit effectively.
Slate ran a bit piece on how many balloons it would actually take to lift a house. The Slate article is good in that it approaches the subject of turning a house into a super-hot air balloon with the same sense of whimsical detachment to a rather silly idea as the film does. That is, from an engineering standpoint, the main conceit of the film is vaguely plausible, but tremendously impractical.
Of course the physics aren't the point. This is a movie about a love for adventure in the young and the old. The flying house is just a vehicle (pardon the pun) for the story, which is why it's an effective conceit.
Further, it adds to the story. Had the old man simply flown and discovered the kid as a stowaway, the sense that he was searching for one last great adventure would have been lost. His character was so effective because he was outwardly a tired, old man, but inwardly young at heart, someone who still has what it takes to hunt down one more elusive dream.