Very good movie, the 70's were Lucas at his most creative. It's a very slow moving film -- but the film has many interesting points: consuming just for the sake of consuming (those blocks that they buy, only to leave the store and throw them away), or the god that they get answers from in a booth.
No spoilers, but my favorite part is the ending -- more specifically what happens during the final moments of the escape, plus that great final shot that continues behind the credits.
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For the DVD, he decided to include CGI in the movie. The only time this really stuck out is when that electronic device "relieved" Robert Duvall -- in the original without it, surely you can tell that Duvall is doing something down there...
Finally, on the DVD Lucas says during the end of his commentary regarding the type of small scale film THX 1138 is:
"it's probably the filmmaking I'm gonna go back to someday. It's a much more interesting style of filmmaking than I currently find myself in..."
"But these more sort of slightly offbeat movies are really where my cinematic heart is."
That was recorded around '02 or '03...