For some of us at some times in our lives, having a relationship with two people is less work. It requires much more communication, better scheduling, and much more attention to your partners' feelings ... but that might be a good investment of time anyhow, and often gets overlooked.

I find that having multiple partners helps me appreciate each partner much more, for themselves -- it's easy to mix up how much you love just having a partner and being loved, with how you actually feel about that person. Poly gives you the distance and contrast to see your partners clearly, and that can be really special.