I think it can work for a lot of people. It didn't work out so well for us. My FWH took one a couple of years ago and passed, even though he was lying. On our DDay in May 2014, he admitted he read several articles on the internet about how to pass the test and surprisingly the techniques worked. I guess this is the reason polygraphs are not admissible in U.S. courts.
He is a pretty calm, not-very-emotional guy by nature, so the test evidently wasn't very difficult to beat. Going into the test, he wasn't sure whether he would pass or fail. His passing the test meant our true DDay was postponed by 2 years.
Don't get me wrong, I think they can be a valuable tool. I probably wouldn't give advance notice if I were going to make my spouse take one. I wish you luck on this rocky journey!