The first 10 minutes of Up are flawless; the final 80 minutes, close enough. (Though, note this: Do not see Up in 3-D. It's inessential to the tale and altogether distracting.)
New York Magazine:
By all means, see Up in its 3-D incarnation: The cliff drops are vertiginous, and the scores of balloons--bunched into the shape of one giant balloon--are as pluckable as grapes.