This is a science fiction comedy that is more imaginative than most of Hollywood's SF and funnier than most of Hollywood's comedies.  It even makes Will Smith tolerable, as long as you're not asking him to carry the scene by himself.  There's exciting action, and the story throws you a good set of surprises.  The way that the kookier ideas of flying saucer nuts are taken seriously is a hoot for those who have familiarized themselves a bit with that subculture.  Yet, there's a lot of Hollywood formula still left in there.  And I mean a lot.

But any movie that can get a good half-minute of laughs just from people quietly filling out forms, is a film that knows its comedy chops.