"Let Go/Don't Let Go"
First, the important stuff: Go.
Don't even hesitate. This is another of those Pixar films that not only entertains, but pushes the form of animation, the more specific discipline of computer animation...and basic film language.
You do not have to see it in 3-D, as the effects are subtle, though expertly done. 3-D does not make or break "Up" and I suspect it will be just as lovely and dimensional on a cyclopian screen (in fact, it might even be better, as the provided 3-D prism glasses tend to mute the film's Maxfield Parrish-like color pallette).
Though just as rollicking as other animation films, "Up" stays somewhat down-to-Earth—no super-annuated cars or toys, no anthropomorphic mice (however, there are talking dogs, thanks to their master's creating speaking collars for them, in a situation that recalls "The Island of Dr. Moreau"—I kept expecting them to break into "Be Our Guest" at some point), and pains have been taken to keep the natural world natural: water-falls feel wet, however improbably they may be, you can practically feel the spray in a fog-bound scene, sunlight lazes across a wall convincingly, and vistas of escarpments or clouds seem picture-perfect.* It takes your breath away.
But there's a maturity to "Up" in its story-telling that's quite unlike any other Pixar film before it, not that the kids will care. As with the previous "Wall•E," the opening sequences are the killer, as directors Pete Docter and Bob Peterson map out the life of Carl (Edward Asner) and Ellie Frederickson, two kids with a mutual passion for adventure, dare-devil Charles Muntz (Christopher Plummer), and eventually each other. The sequence is done with a moving simplicity (with a stunning attention to detail) and no dialogue, just images telling the story of a marriage in all its depths. That sequence haunts the entire movie, not only for its subject matter but also for the task of trying to top it.
It gets enticingly close many times** and when it doesn't you're usually roaring with laughter,*** but the rest of the movie seems almost prosaic in its predicaments and complications. You don't want this one to end like your typical chase movie, and even though it does, it does so better than the vast majority of them. Even while the hi-jinks ensue you can't help but think that even these situations work best as allegory in setting up the big gambit of the movie, with precipitously floating dirigibles and houses and many, many situations of making the vertiginous decision to let go or not let go.
For technique, creative thoughtfulness and a painter's eye, Pixar's team of magicians and imagineers are unsurpassed in continuing to influence the art of film.
"Up" is a Full-Price Ticket
Update: Glenn Kenny has a concise "halleluia" for "Up" at "Some Came Running" that addresses some of the many joys encountered therein, but also touches philiosophically on the critical ennui of writing about the latest Pixar release ("Ho-hum, another brilliantly conceived and executed Pixar film"). There's no pleasing some people ("Hello, Stephanie Zacharek and Joe Morgenstern!" Perhaps their reviews were "inspired" by a bad meal at Cannes with a snooty waiter...) who have become so jaded with consistent quality that they wouldn't know A Great Movie if they tripped over it in a darkened theater.
* And for me, the favorite sound design element is the sound of the balloons above the house bouncing together, sounding like rubber petals.
* Including a "taking flight" sequence that is among the best in cinema
*** Best line: "Well, that won't work..." The adults in the audience laughed for a full minute. You have to be there.