This is a great post and makes me want to watch the Taming of the Shrew. I do want to quarrel with your characterization, though, that "the old medieval and Renaissance way of looking at love is as something that maintains the hierarchies by which society is structured."
It's certainly the medieval and Renaissance way of looking at love -- of a certain kind -- as something that can maintain those heirarchies. Particularly, say, love of God, or the love involved in fealty. But it isn't the characterization of romantic love -- by which I particularly mean heterosexual, unconsummated, non-marital love, the aspirational affective relationship between a man and a woman who've not yet mated, which is what's at issue in Shrew -- that I'm most familiar with in medieval and Rennaissance works.
Rather, it seems like romantic love is usually a destructive force which at least potentially puts the social heirarchy at risk. Courtly love is supposed to be unrealized and platonic, but it's distinctly an unrealized extramarital affair, one that if realized would lead to bloodshed. Guinevere and Lancelot's love does not reinforce the social order, and much more time is spent on that love, in the Arthurian saga, than on Guinevere's love for Arthur; indeed it seems to me that it's more likely to be a modern version which would cast Guinevere as conflicted and dwell on her emotional marital love for Arthur. In the medieval context it seems that what is important, and at risk, and morally decisive, is her pledge to Arthur, emotions having little to do with it.
Where romantic love is not a tragic or potentially tragic force, it's a usually comic one, lampooned as a reason for people to make fools of themselves, as in the commedia dell'Arte or the mortals' hijinks in Midsummer Night's Dream, etc., which is another way of acknowledging its disruptive nature -- it causes otherwise sensible people to act in foolish, immoderate and risky ways.
It actually seems to me that the story of romantic love -- a premarital affective passion -- leading ultimately to marital happiness is more of a modern innovation -- if I were a Marxist I would say you get it when, say during the regime of Jane Austen, the bourgeois have become the dominant class. It seems like our myth, the drama of our Hollywood movies and the paperbacks in the aisles at Wal-Mart, is that the love which initially seems disruptive -- in which the lovers "meet cute" and start as combatants, or in which the brooding Mr. Darcy or Rochester seem forbidding and dangerous -- turns out to be the key to stability and bliss. Love not only conquers all, but restores all to social harmony: coupled status, regularly available sex, a house in the suburbs and a really great nanny. (In the medieval, omnia vincit amor was bittersweet, part threat). The contemporary Hollywood Darcy or Rochester, or their Wrong Guy competitors, is less likely to actually harbor any real threat than the Austenian or Romantic version did -- Hugh Grant may have been a cad and the Wrong Guy in Bridget Jones, but he was actually kind of a nice cad, well-meaning, not a Wickham capable of ruining a younger girl or scheming to obtain an inheritance. A modern Hollywood version of Rochester is unlikely to actually have locked a mad wife in the attic -- not if the heroine is going to end up at "Reader, I married him."
Of course, literature is an inaccurate guide to what people really felt, not least because writers are constrained by the need to write about something exciting, which is ipso facto not the typical case; and I am committing the typical error of comparing great old works to average new ones (I did rather like Bridget Jones, but it's fluffier than Pride and Prejudice, to be sure); and you've doubtless read more medieval and renaissance literature than I, so my sample may be skewed.
Still, it seems to me that specifically romantic love, the kind easily confused and mixed up with bodily lust, as opposed to love of God and King, was really seen mostly as a potentially truly destructive force in the medieval and early modern -- one which could perhaps be trivialized in farce, constrained by pious vows of platonic courtly love, or even resolved, in the relief-filled laughter of comedy, into a proper marriage -- but which could just as easily end in tragedy. When, as in Shrew, the lovers end up becoming a socially acceptable marriage, there is the sense of a bullet dodged: a destructive social force, passion, which would naturally lead to tragedy, has been transmuted alchemically into a sustaining social force, the fealty of the vassal/liege relationship between a wife and her husband. Cause for the laughter and relief, and for celebration.
Whereas in the tales we like to tell ourselves, romantic love appears dangerous but is actually safe, and in fact obligatory -- it is an invitation to temporarily dangerous adventure, but at the end, when the hero kills the bad guy and gets the girl, romantic love -- passion -- is in fact the safe and sustaining social force with which he is rewarded. When Mary Jane runs off from her wedding to the Wrong Man to find Peter Parker moping in his apartment and says "Isn't it about time somebody saved your life?" and then they kiss, there's no need for a transmutation of passion into fealty. The kiss, the offer of romantic passion, is the life-saving; it restores the sustaining social force of romantic love whose absence was a threat. Under the rule of the bourgeoisie, romantic love is no longer a dangerous power which can erupt without warning and bring about doom, something to be feared and managed until safely bound; rather, it is something we all deserve and should have on tap, like hot water, refrigeration, and the movies.