Completely agreed. Granted there's some lows too, but the highs far outweigh them.We find ourselves very much happier. For a start, we both experience compersion as a very real thing (for example I have spontaneously come three times during our meets as Lass approaches climax whilst riding our shared lover) and we both love to see the other happy.
It's also an acknowledgement that humans aren't always naturally monogamous - we all, all, look at other people but swingers like to act on it.
This is it, it's natural human instinct to look at other people and eye them up. It's normal.. and as you say, as swingers we just act on it.