Let's get the basics out of the way, first.
Yes, the plot is a bit thin (and can mostly be discerned from the trailer). And yes, the flashback exposition scenes are occasionally obtrusive. And the CGI isn't perfect.
But Tron Legacy has some surprising depth. It occured to me, as I thought about the review, that the title is aptly chosen, as the driving force behind the plot is Kevin Flynn's legacy to his son, and to the world. But more about that in a bit, as I really can't get into it without spoilers.
I have to confess that the eye candy is quite choice, as I found myself saying "Oooh, I want one of those", more than once. The visuals are stunning (I hope to catch it on IMAX after the holidays), although there's an annoying cinematography trick in many scenes where the foreground character is the only thing in focus that drove me a bit nuts at times. And Daft Punk's soundtrack is excellent.
As for the story... It's not perfect.
The movie starts out as you'd expect, with Sam as a boy and his father. It rapidly leaps ahead to Sam as a troubled adult. One surprise is that the scenes at Encom are not just about the mysterious page, but actually include a subplot about how, well, Microsofty the company has become since Kevin vanished, and Sam's unwillingness to take control (despite being majority shareholder) of his father's legacy.
Well, one of them.
The rest is pretty obvious. Sam gets zapped into the grid, fights his way free of the games, finds his father, and has to escape back to the real world. The basic elemnts are very similar to the first film (and there are several callbacks), but the approach is very different.
First, there are some interesting side characters, like Michael Sheen's scene-devouring Castor, who was channeling both Sydney Greenstreet in Casablanca and Joel Grey in Cabaret (although I swear I heard a bit of "Serge" from Beverly Hills Cop at one point), and Clu's sycophantic major domo, Jarvis.
Rinzler, the Boba Fett of the film, says little, but his words (and actions) carry a lot of weight, particularly at the end (when he regains his memory as Tron). Even Quorra, who I suppose could be called Sam's adopted sister (love interest is stretching it) is played with a mix of naivete and strength.
The heart of the film, of course, are the Flynns: Sam, Kevin, and Clu.
Sam, to be honest, is the weakest character, and while he eventually accepts responsibility for both Encom and Quorra (his father's OTHER legacy), it's hard to imagine him any good at it.
Clu is not as great a villain as you might think, despite the traditional Triumph Of The Will speech to his army. He's a tragic figure, not only as the neglected son, but also because his entire personality is based around what he was created to do... build a perfect system. Perfection, as Kevin himself notes in a critical scene, is not a viable goal.
It's hard to draw a bead on him. Despite being a geek from the 80's, for much of the film he's more like one of Bridges' earlier roles, The Dude from The Big Lebowski, complete with lines like "you're harshing my zen dude."
Later, he busts out a cool hooded black robe, and goes into what I call "Obi-wan Flynn-obi' mode, where he basically remains for the rest of the film, with some backsliding to groovy hipster. And, at the end, he's...
How can I put this...
He's The Creator of The Grid. And what he brought into the world... he can take out.
The ending is somewhat of an anti-climax. For a Disney film, it's also not quite what I expected, given that Kevin sacrifices himself to allow Sam to return to the real world. While there are some sequel hooks, there's also a sense of letting go of the past and becoming a man (which, given that Sam is supposed to be 27, is probably overdue).
Still, while it may not be a great movie, it is a fun one. And sometimes, that is enough.