All these negative comments are from GOVERNMENT AGENTS trying to hide the TRUTH that this movie reveals and that the Bilderberg Group and the NEW WORLD ORDER don't want you to know!!!!
Very good movie. It's obviously an adapted stage play, and I think Friedkin's and Letts' later collaboration on "Killer Joe" is superior, but the dialogue and performances from Judd and Shannon are excellent, and the film does a good job of producing an atmosphere of paranoia and insanity.
I'm not sure what the "secret" is that the poster below me is referrring to:
the movie seemed pretty clear that both Peter and Agnes were imagining the bugs and helicopter noises. Particularly at the end when the house is shaking with the noise of helicopters and lights, and we cut to Jerry outside and there is no noise.
If you enjoy this movie, then I would recommend "Martha Marcy May Marlene", which has a similar dialogue-driven atmosphere of paranoia.