What follows are the non-situation-specific observations (theory? speculation? humbug?) I just made in response to a friends-locked post in someone's journal. In the spirit of open source living, I thought I'd share them publicly in the hopes that some may find them useful or insightful.
In an arrangement like marriage, it's important for everyone involved to know exactly (or at least generally) what they expect out of the relationship (intrapersonal awareness) and what the other people expect (interpersonal awareness).* Since marriage usually is the sort of situation that's harder to get out of than get in to, tackling expectations, concerns, boundaries, and goals in advance is a lot better than discovering unreconcilable differences part way through. Polyamorists can have an advantage in such matters because they're used to similar discussions. But since each polyamorist marriage tends to be unique, it's not easy to find actual or idealized examples to follow. What form will commitment take? How can the involved parties evaluate the success of the relationship? If things don't work out, what should happen? Stick it out and let it end are both valuable commitments. I think interpersonal awareness of which to expect is key.
When considering marriage, cohabitation, and other situations it's important to weigh mundane concerns with transcendent ones. Even among people who are deeply in love, enough surface conflicts like chronic mess can make living together unwise. On the other hand, my parents have been arguing about that (Point: This crap is unnecessary! Counterpoint: No, I use that!) for nearly 40 years and it doesn't threaten their relationship. There's a balance between putting up with a partner's quirks, loving a partner despite their quirks, and setting enough boundaries on quirks so that everyone's quirks have room to live.
* I can think of another important awareness: extrapersonal. Ironically, a partnership doesn't usually have to work too hard to figure out what to expect from society even though they have less control over how those expectations are met than they do over the other two aspects.