The movie may date from 1970, but its message is far more significant than a far echo of its decade.
Not as smart as "Solaris" or "2001: A space odyssey", it nevertheless captures human determination, and the sheer will to be free, no matter what's sent our way. Robert Duval plays his role (THX-1138) to a degree of perfection: introvert, yet boiling with an inner rage at all time. This rage, he uses to exact his plan to try and get out of this futuristic hellhole, and with some added CGI (Lucas, can't help himself), the movie actually benefits from having a nice scope and greater visuals, though I wonder what the original film looked like.
Special features are very entertaining, insightful and come in great numbers, culminating to almost 3-4 hours worth of visual documentaries, plus a commentary track. It is hard to ask for more in this case.
Not the "be all end all" of sci-fi movies, THX-1138 has enough smarts, ingenuity and pacing to be called a film. And a classic film, at that. Its message will most likely be as resonant 50 years from now as it felt 40 years ago.