Actually, now that I have reached the portion of The History of Sexuality where akrasia turns out to be the opposite of enkrateia, the usefulness of the concept has been magnified.

The most pertinent sentences: "Enkrateia, with its opposite, akrasia, is located on the axis of struggle, resistance, and combat; it is self-control, tension, "continence"; enkrateia rules over pleasures and desires, but has to struggle to maintain control... As an opposite, akrasia is not, like immoderation, a deliberate choosing of bad principles; it invites comparison, rather, with those cities that have good laws but are incapable of enforcing them; the [akrasic] individual lets himself be overcome in spite of himself, and despite the reasonable principles he embraces, either because he does not have the strength to put them into practice or because he has not given them sufficient thought: this explains why the [akrasic] person can come to his senses and achieve self-mastery."

That's probably old news to you, but it was helpful to me. :)