One consequence of this is that friendships can be quite unbalanced and I won't think it's terribly important.

I really like the fact that this fits into the theory. I've never been one for 'keeping score' of how good a friend I am to X, or how good a friend X is to me, and even less do I like the idea of comparing those two 'scores' and making some kind of value judgement about the relationship based on the comparison. As you say, if it makes me happier to be friends with someone than not to be friends with them, what more do I need to know?