Is this article about monogamy (1 marriage partner for life) correct?

a href="http://www.takeninhand.com/node/405" rel="nofollow"http://www.takeninhand.com/node/405/a says that the best you'll ever have is with your marriage partner, and that promiscuous people are unhappy. It says monogamy is the way to be ually happy. Is this true? This is sort of a survey question. I really want to hear from people that have been there and done that.