Probably the weakest of John Carpenter's films (that I've seen, anyway), but still pretty awesome. The big green cylinder really does look menacing, and the scene where the guy is getting eaten apart by bugs is great. Satan typing in all caps like a 14-year-old forum troll, not so much.
If anyone's interested, I made a terrible song based on samples from this movie, "Conscious Neural Interference", and you can find it here:
http://www.myspace.com/thehanglyman