A really great film, one of Connery's better performances (not his best, which is in The Offence I reckon), but he creates a really sympathetic and real character, not a superhero, just a guy who has just had enough and decided he is not going to toe the line any longer.
Despite the futuristic setting, it's just about the least 'sci-fi' of any sci-fi film I've seen. In may ways it could just as easily be set on an oil rig or an antarctic station, but somehow the extreme remoteness and isolation of the setting does come across and magnifies the tension, and the effects and model work definitely stand the test of time.
It looks great, has excellent acting and it thrills. If you never saw it, you have to check it out, it's a 'forgotten classic'.