UPDATE: Lileks' review:

In the end it’s difficult to describe without spoiling it, which is why I’m not going into more detail. But since everyone talks about misting up at the end – or flat-out sobbing, depending – and yes, it’s a killer. It’s a surprisingly long goodbye that gives each character their due and closes the story with gentle grace. (And they promptly pick you back up and makes you laugh with an extended credit sequence.) For me, though, the most effective episode came earlier, in the final Scene of Great Peril. All of these movies have moments were everything seems lost, when escape seems impossible, when Evil seems about to triumph, and of course TS3 had that scene. Usually the heroes are just about to do something before they’re saved, or they make one desperate last lunge that turns to be the exact right thing to do, and if they have a moment of doubt and fear it lasts one beat, two beat, three – SALVATION!

Not this time. Again, I don’t want to spoil anything, but in retrospect it reminded of “Titanic,” only inasmuch as the emotion in TS3 were absent from the sinking of the ship. Cameron uses emotion to explore the possibilities of computers; Pixar uses computers to explore the possibilities of emotion.
You’ll know what I mean when you see the scene. If you saw, you know, right? The expressions, the hands, the dread, the quick and necessary assumption of acceptance. It’s a Bambi’s-Mom-is-Shot moment but much deeper, and I don’t think there’s anything like it in the Disney canon.

It's funny: you can describe the scene in synopsis form using maybe three brisk sentences. The plot of it is simple; the staging is nonspecific. But it's the execution that makes a great movie (or a Pixar movie, but I repeat myself) what it is.

Someone of the Michael Bay or Brothers Wachowski school would flesh out the scene by building it up with intricate details of character movements and actions, stringing them together in a Rube Goldberg machine of direction and cause-and-effect until you can't summarize the scene in those few brief words, but rather a thick sheaf of stage directions and storyboards covered with arrows and notations. But the way this was done, it's 10% concept and 90% all the little things that fit in between, things that can't be captured on paper: character and camera work and color and pacing and what for all the world feels like volcanic heat on your face.

They're relentless, these Jobsian people. And never once do they give the impression they're making it up as they go along.