It's like, one thing that he was adamant about from when he dumped me the first time and through all the time we were trying to get back together, was that he didn't want us to be in an 'our lives revolve around each other' relationship like we had previously seemed to be heading for. But a week later, when he was actually 'in a relationship' with her, he was really upset that my romantic life and plans no longer revolved around him. And then he wanted us to be exclusive suddenly, despite still (to my knowledge, and he refused to answer when I challenged him to resolve the disparity) wanting to be in a fun-and-no-responsibility relationship with me. And wanting to 'take it slow', which, from what I've pieced together since, seems to have been intended to mean 'be fully committed but spending absolutely no time together, exchanging no affection, and having no plans for anything changing, ever, while I work out whether I even like you any more'.
At the time I was trying to work out if it meant 'wait for me to get my shit together' and acting accordingly, but when I was asking 'do you want me to just wait for you to be able to think straight about this, because I can do that?' he wasn't forthcoming at all. (And kept fucking the one person I really wasn't okay with him fucking right then, which I took as an answer in itself until he finally gave me the spoken one.)
I've been in a 'fully committed, no time together except for when he deigns to allow it, exchanging no affection and having no plans for anything changing, ever' relationship before. It was the one that put me off of the words 'boyfriend' and 'girlfriend' and 'monogamy'. I've gotten over the boyfriend/girlfriend thing now, but'monogamy' still says to me 'I am your primary source of affection, physical or otherwise, and if you are unhappy with me withholding it then you have no recourse whatsoever, because I shall get offended if you suggest I'm doing anything wrong'. That was a long-distance relationship in which I was being treated like a robot-girlfriend - wanted when it was convenient (press the right buttons and sex comes out), but expected to hibernate when he wanted to play computer games for hours. Like, he was so sure that I'd wait around until he was ready to start living, that he never started until long after I'd left. I mean, we had our future children's names picked out, so I wasn't going anywhere, right?
I'm done with being a status-symbol-girlfriend, or an in-name-only girlfriend. Especially with exclusivity - there are things I require in a relationship, and affection is one of them. If a guy wants to be exclusive with me, he damn well better be spending at least most of his nights sleeping in my bed - I'm at least experienced enough to be able to see 'don't see anyone else, but I won't see you either' as the joke that it is.
I'm happy with my current arrangement - I can see it changing in a number of ways as time creeps on, but I'm fairly easy with regard to that. The optimal relationship-configuration for any number of people will depend on their individual needs and preferences, which is why these things need to be negotiated and talked about rather than assumed or guessed at. The Relationship Escalator isn't a given, but it is an option. Closed networks are options. Open networks are options. Living together is an option. Living separately is an option. Having kids is an option. Remaining child-free is an option. Pursuing small happiness is an option. Pursuing big dreams is an option. But you've got to talk about it, or no-one ends up happy about the outcome.
Unless they're really lucky, I guess.