You get to see "It" fairly early. The actors here that I'm most familiar with are Dabbs Greer and Marshall Thompson.
This film is said to have been the inspiration for the film Alien.
Watch it here from goodlevideo:
1000 Misspent Hours calls it "an extremely solid film". Moria says this film "really invented the concept that Alien turned into a subgenre – of aliens stalking crewmembers through spaceship corridors." ClassicSciFiMovies says it
holds its own as far as a story goes. The very spartan-ness of the set and costuming in It keep such accessories from getting in the way of the story.
8/23/2009: SFSignal features this film in their Sunday Cinema post today.