I got the chance to see Tron: Legacy recently. I have to say, I was rather impressed with how much better the look and feel of this sequel was when compared to the original Tron. The original movie was considered revolutionary at the time, but I don't think it holds up very well.
Fans of the original movie will be pleased to see that the new movie features updated versions of the classic disc battle and light cycle scenes... one of my favorite moments came when the two things were combined, something you never saw happen in the original. The 2010 light cycles are capable of operating on multiple levels, going up and down ramps, and even jumping over people, leaving behind a deadly ribbon of light everywhere they go. (The 1982 light cycles are practically two dimensional by comparison... they never go through the air, and while on the game grid they can only move straight ahead or turn exactly ninety degrees to either side.) There are updated version of other classic vehicles too, along with a few entirely new ones... there's even a dogfight between light jets at one point.
Another thing the new movie has that the original doesn't: an awesome musical score by Daft Punk. Their music breathes life into the movie in ways that are difficult to explain... the special effects (and Olivia Wilde's cheekbones) are nice to look at, but it would all feel pretty cold and dead without the music. By the way, the musical duo has a cameo in the movie; they appear as the two DJs playing music at the End of Line Club.
It was a bit tough to make sense of the plot at times, but you could easily say the same of both films; however, the filmmakers did such a good job of making Tron: Legacy feel like it was happening in a real place that it made the absurd premise of the movie a bit easier to swallow, and it somehow allowed the film to skate around gaping plot holes by calling them "miracles" and "biodigital jazz." It also helps if you like Jeff Bridges, which I do... his own personality really comes through quite a bit in his role as the older Kevin Flynn. (It might help if you like Garrett Hedlund, too... but I really don't know him from Adam. One of the problems I had with the movie was that Kevin Flynn's son Sam actually isn't very likable when we first see him as a grown man, and so a lot of the real-world stuff at the beginning of the movie ends up feeling kind of pointless.)
One other thing I'll add, without trying to spoil anything too much, keep an eye out for one villain in particular who bears some very distinctive markings upon his chest.