The honesty and respect! And lack of taking offence at someone else's boundaries, but instead everyone genuinely just trying to do right by each other.

I accept this may not be everyone's experience, but I have been blown away by that part of my experience.

Me and husband have recently opened things up a bit, although at the moment only really on my side (his choice). So we've been to a swingers club and now I'm seeing another woman in a fwb situation.
People at the swingers club were all so friendly and super respectful and repeatedly checking in to make sure I was OK with what was happening.

And now I'm seeing this woman, we've had so many conversations about boundaries and what both me, her, her (male) partner and my husband all need from the situation. And at no point has there been anything other than unquestioning understanding and acceptance of what everyone is happy with and what everyone needs.

And I love that! I think when 'normal' relationships start and evolve, there's not always that expectation that these conversations need to take place and so things can get messy, people can get offended. An example - my fwb has told me that she isn't comfortable with PDA, even when there isn't actually anyone watching. And that's totally fine and I'm glad she's told me because I would hate to make her uncomfortable. But I feel in a 'normal' relationship, things like that aren't always talked about and so people can take offence/people can feel pressured into doing things they aren't comfortable with.

What's everyone else surprise thing they like about non-monogamy?