I never saw the original Tron, however based on a trailer I looked up, it looks like it featured one of the earliest uses of CGI graphics (and blocky ones at that).
Now, a sequel is poised to be released one year less thirty years after the original, complete with original star Jeff Bridges returning.
From the looks of the trailer, it is obvious that CGI has advanced A LOT in three decades. The trailer is made up of a single chase scene that shows off the new digital world.
The film is scheduled to be released in 2011 and it will be shown in 3D. In the meantime, I should probably track down a copy of the original.