What are your thoughts on polyamory?

Polyamory is the practice of having more than one loving, intimate, stable relationship at a time with the full knowledge and free consent of everyone involved, sometimes described as consensual, ethical, or responsible non-monogamy.

Polyamory (as opposed to polygamy) is a more modern outlook, grounded in such concepts as gender equality, self-determination, free choice for all involved, mutual trust, equal respect among partners, the value of love, the ideal of compersion, and other mostly secular ideals.

(http://en.wikipedia.org/wiki/Polyamory)

If you’re interested in reading more, Newsweek just published an article about it (http://www.newsweek.com/id/209164).

I, for one, am in a committed relationship with someone (2 years now and going strong!). that person is married, and their spouse is also dating someone else. While there are difficulties, there aren’t really more than in traditional relationships, and we are all very happy with the arrangement.
What’s your take on this?