Actually, come to think of it - and I know I might be inviting scorn from some horror fans - "The Exorcist" is far from showcasing this director's skill. Yes, it's a well made film, but I found it nowhere near as scary or as effective as it is claimed to be.
It's not as well crafted as "Carrie", nor as frightening as "The Serpent and the rainbow", nor is it as disturbing and unpleasant as "Texas Chainsaw Massacre".
And while "Bug" is not a horror film, it does a far better job in showcasing his directorial skills. The camerawork is great and the story, while far from being original, is properly rendered(even if it offers a rather lousy ending), the performances are solid and, most important, the resulting film is not just another silicone product on the market.
Within the past twenty years or so, there have been dozens of films tackling on "conspiracist" grounds.
But few of them chose to dissect their mechanisms instead of wallowing in their juicy narratives. And "Bug" does just that. It takes your casual conspiracy theory(in this case, one involving bugs) and dissects it. Only it doesn't do it in the academical way(fortunately. Otherwise, it would have really been a tedious experience). There is no strong rational side here, cause there is no need for that: it would have gotten in the way without offering much help.
Instead we watch Peter play out his conspiratorial fantasy, we watch that unfold, we see how it works and how, pretty much like a parasite, moves on to another vessel. Cause this is what happens in the end.
Conspiracies often take basic inconvenient truths and exacerbate them to the point where they catch apocalyptic proportions. And they do this by using narratives, because people are suckers for narratives. This is how they get to so many. Every good conspiracy theory, no matter how crazy and illogical is, in the end, offers a juicy narrative. It's a psychological con-job. And this is where "Bug" shines, in how accurate its depiction is. And for this alone, the sloppy ending is forgivable.
My two cents: 4 out of 5.