Like you, I am in favor of a new paradigm for loving partnerships, one that does not require two people to be the be-all and end-all for each other. And the philosophy as published by intelligent people seriously pursuing or exploring the possibilities of a polyamorous lifestyle sounds promising.
Often, though, "I'm poly" seems to be another way of saying "I'm into lots of sex with no commitments." Which to my mind represents hypererotic hell--the ultimate in loneliness. Honest mutual love and ever-deepening levels of emotional intimacy are the best things about any sexual relationship.