Original comment is at Love, Joy, Feminism.

Some benefits I see in non-traditional emotional/sexual partnerings between adult equals (not comprehensive):

1.  Partners get to make rules that apply to their specific situations.

2.  Relationships are based on honesty, respect, and clear communication.

3.  Partners take on the responsibilities that best suit them while also being encouraged to develop skills to deal with the responsibilities they aren’t quite proficient at.

4.  Partnering is exactly that, where individuals are encouraged to be their best selves while also loved and understood for their less than best selves (not an excuse for abuse, manipulation, and/or coercion, though).

5.  Partners are seen as opportunities for love rather than expectations of disappointment.

6.  Partners are encouraged to be both self-sufficient and vulnerable, not controlling and needy.

Addendum:

7.  Knowing for certain your partner(s) actually want(s) to be with you.

I deliberately un-gendered the partners and non-specified the relationship styles to make the benefits apply to the broadest possible situations and individuals.