People who are or have dated more than one person, how did it work out?
I've been with a lady for two years and recently started dating her new boyfriend. We all consented to the relationship and so far, it's going good. I've also heard from some people though who used to date many people that it didn't work out so they decided to date monogamously.
I have been dating non monogamously for something like 15 years now. It's not without it's unique challenges, but most of the problems people have with polyamory are actually problems they have with monogamy as well, it's just easier to avoid dealing with certain things (like relationship insecurity) when monogamy allows people to pretend they aren't happening or to lionize expressing them negatively (as jealousy, for example).
In my opinion, even if you decide it's not for you, exploring non monogamy is very likely going to give you better tools and healthier perspectives than you'd have if you remained "safely" monogamous your entire life.
It's definitely been working out for me, for years now. I have two boyfriends, they get along well and also both date other people. There were a few growing pains of course. Overall though, smoother than expected!