It is absolutely that bad. I took the test for a job at the NSA. I had nothing to hide. I am/was the most straightedge person on the planet.
I was strapped to the machine for 3.5 hours while they asked me the same 6 questions at least 8-12 times. Every time they told me that I was flunking the question regarding "falsifying information on my NSA security forms." I falsified nothing.
Once they detect a problem they shift from Mr. nice we'll have you in and out in five minutes guy to an actual interrogator. He left me alone in the room to sweat it out for 20 minutes. He kept going back to different things on my forms trying to catch me in a lie. He gave me all the lines about how he was just trying to help playing the ridiculous good cop/bad cop game with a guy who just wanted to do some interesting math not blow up the country.
I wasn't lying about anything by I was treated like a criminal. It was honestly one of the worst experiences of my life. I never found out if I passed or not as I ended up working at a DOE lab. If they had told me that I had to come back to try again I would have withdrawn my application. I wasn't lying the first time, why would the results be any different the second. And with the dogs sniffing in my car and the insane psych exam the whole culture seemed toxic and paranoid. I work at an NW lab now and IT has looser security than the NSA interview site has.
The machine does not work, end of story. And any propaganda video that tells you the polygraph is a painless procedure is a complete load of crap. A friend of mine later had a similar experience so I know it wasn't just me.