I really like Harrington, she's thoughtful and also a very clear writer who doesn't stoop to games.
It's interesting about her view of balance and progress, and I hadn't twigged those were her views, but it's probably why I find so much of what she says sensible. The idea of materialist progress, especially in the moral realm, is one which IMO causes a lot of errors in logic. Was it Bertrand Russel or one of the other philosophers of that period who said that this was a holdover from Christianity, but oddly translated into a kind of faith about social progress in the material world. Hegel plus Marx, I suppose.
Anyway, as soon as you jettison this sort of faith in progress (to what) and the view of time that comes with it, political thought has to become much more cautious, and right answers seem much more difficult and provisional, restricted to a particular place and time.
I also think the idea that liberation and control are a balance is really important. The basic point, to me, is that if you want a society with a lot of legal freedoms, people need to have a lot of interior control, if you don't want chaos. And how do you create people with that sort of interior control? It's not easy, and not really amenable to very easy-going sorts of childrearing or even education. Alterably, a society with strict legal/social controls can allow people to have a lot of freedom of thought.