I first saw this film accidentally when they showed it on TV and I was up far too late... I really lucked out there though. It's truly incredible; from the location (as isolated as it's possible to be on this planet; it made "the abyss" look like ET in the council swimming pool), through the interesting characters (Keith David is especially good as the reactionary Childs -"What if we're wrong about him?" - "Then we're wrong.") and the effects (more yucky than Alien).<br /><br />Moreover, however, the real tension and fear in the film has nothing to do with the effects. It's the people you start being scared of; knowing that one of them may - or may not be - "All they appear to be". It's certainly got the feel of "who goes there?".<br /><br />The soundtrack is great; it really plays up the isolation, fear, and gravity of the situation.<br /><br />Finally, the epilogue scene really, really cuts. Even more than the "But then again who does ?" punchline of Bladerunner. Enough said.