No one should see Tron today for the visual effects, the acting, or even the plot. What you should see it for is the great ideas it presents that endure even today: the notion of artificially intelligent (AI) programs, the said programs fighting each other, users becoming programs, and all of this happening in a virtual reality that is quite imaginative given the time the film was made.
The film is about a meta-computer program, the Master Control Program (or MCP, voiced by David Warner), a chess program that is reincarnated into one that controls all other programs, and has ambitions to take over the world. When Kevin Flynn (Jeff Bridges), a hacker, gets too close to thwarting its plans, he is "beamed" in the computer as Clu and risks facing destruction by the MCP, along with the security program designed by his friend Alan (Bruce Boxleitner), called Tron. Together Tron and Clu must prevail against the MCP to save the future of humanity.
The movie takes an extremely anthropocentric viewpoint, and at the end points to a flaw in humanity's thinking: if true AI were to be achieved, it would look more like what we saw in The Matrix than in this film. The reason for this has to do with treating the apparently sentient programs as nothing more than slaves, objectifying them. Any well-designed self-evolving program will reach a point where it will desire a position more loftier than that.
Tron is a must-see for any pop-culture afficionado. Besides, how can you resist a movie where a character who plays a computer program goes by the name of Ram?