I wouldn't say this is one of the all-time great sci-fi films, but it does very well with what it has.
The time travel machine (and the reasons for using it) is more plausible than any other I've seen in movies or TV, and the story, though not fast moving, does keep you interested.
However, I was disappointed by the "Soylent Green" type revelation at the end; it wasn't in character with the rest of the film (though it was cool in a creepy kind of way... I know that if I had seen this movie when I was a kid, that last scene would have stuck with me forever, though I probably would have forgotten the rest!)
The time travel machine (and the reasons for using it) is more plausible than any other I've seen in movies or TV, and the story, though not fast moving, does keep you interested.
However, I was disappointed by the "Soylent Green" type revelation at the end; it wasn't in character with the rest of the film (though it was cool in a creepy kind of way... I know that if I had seen this movie when I was a kid, that last scene would have stuck with me forever, though I probably would have forgotten the rest!)