My wife and I tried swinging because we knew we wanted something more than we had. Casual sex always left us feeling a little empty afterward. We were GOOD at swinging, in that we never got jealous and always had a good time with other partners and seeing each other with other partners, but we wanted that connection with the people we were in bed with.
Enter polyamory. Enter a whole new set of problems. It's easy to find people we both want to (or are at least willing to) have sex with. Being intimate and involved in a loving relationship is a whole new ball of wax.
We could never go back to swinging, though. It's the feelings that are far more important to us than the sensations anyway.