Man this movie scared the CRAP out of me when I was a kid. I think it was really well done, and the fact that you don't really see anything most of the time, other than say, a bush moving, or a rumpled sheet, really added to the creepiness. Also considerably adding to said creepiness was the score by Bernard Herrmann ( one of his last ). Neat film, hear there's a remake... Larry Cohen's movies were always great, and you can tell that even with obvious budget limitations, his creativity really carries this movie. As a matter of fact, the reason you DON'T see much of the mutant is probably due to those same limitations. The sequels, though somewhat interesting, did not capture the eerie suspense of the original.
Review of It's Alive
