I quoted Nan Boyd in my last post about desperate attempts to save the foundations of sexual nationalisms. What I mean, more specifically, is that I find the attempts to save a clear-cut binary sex, or gender division rather funny: no clear binary exists, not in a biological sense (there's the pesky intersex, plus we don't exactly know how bodily sexing goes, and in order to have a clear binary, you really do have to know), and certainly not in a social sense - just go see your local genderqueers for a proof.
Moreover, there are some other fundamental problems, too: when we speak of biological sex, we are applying human-invented categories to phenomena we observe in nature, and it's pretty clear to me that the categories themselves are socially constructed, too - they're sure rooted in biology, but they're just as deeply rooted in human needs to categorise and dominate the world. There's no disentangling the social from the biological, or vice versa.
Which brings me to my point: sex and gender are interrelated in multiple ways, and we don't have a complete picture of how this happens - and it may well be we shall never have the complete picture. You see, when we're observing something outside ourselves, we have to classify it to be able to express the observations to anyone else in language - and when we do this, we're already bringing in the socially influenced apparatus of language, and, in effect, shall never have such a thing as pure, unbiased results. We can certainly try, and I'm not so pessimistic as to think we'll always be badly wrong, but I am confident we shall never get it totally right. We'll always be somewhat wrong. Strangely enough I find the thought comforting.
My second point is, social construction is on its own insufficient to explain sex or gender. If all gender really is socially, and socially only constructed, why does it fail so badly? Why does the construction make such a botched job of building two, and two only, genders and sexes? Why do people rebel against it? And on the other hand, why so many people do accept one of the two socially sanctioned genders (myself included)?
What I see, in my culture (big city, middle class, educated - I'm basically your privileged white girl except for the trans plus queerly sexual bits) is people who mostly toe the line when it comes to gender. They seem to be mostly happy with their sexed bodies, too. This is not to say they're happy with the very real inequalities between sexes and genders, but I think you'd be hard pressed to find a substantial amount of women, or men, who are intensely unhappy about there being sex/gender combinations such as "women" and "men". The unhappiness lies - or is made to lie - rather solidly in the margins: those who do not want to, or cannot live the binary in the way they want, or need to.
Thus, the (political) problem of sex and gender is manifold: part of it is just plain ol' oppression - patriarchal, cisarchal, classist, the lot. Part of it is that binary sex and gender really seem to fit a large majority of people, and thus it's rather hard to see a future development where sexes and genders would be significantly more complex, and would thus open up the possibilities more easily for those who need or want them. Thus, a wholesale queering of everyone and everything is, in my opinion, an utopia: all very nice, but it's not going to happen because there's insufficient demand, and the benefits are not tangible enough for the majority to get really excited about. Heck, there's very little tangible benefit from seriously queered gender and sex to me now, as it is.
Going back to theories, a large part of the reason why current theories on sex and gender are so insufficient in my opinion is that there's so little research into how gender and sex works for the majority. So far, almost all research into sex and gender has focused on the "non-normative", on the "abnormal" bits, and as far as I can see, majority sex and gender has largely been ignored - it has been taken for granted, as if it was a simple question: "duh, everyone knows what a woman is". As if! I'd really like to see, say, a majority feminist organisation, or our national health system, really dig into its own practices of sexing and gendering - how does it do those, who are included in practice, who are excluded, why, what are their solutions to the practical problems of sexing and gendering that happens on the margins - as far as I can tell this isn't even documented, let alone analysed. The results should be interesting (probably shocking, too, in many ways).