I've been working on this section quite a lot, trying to improve the flow of content (which in the prior revision is a bit of a mish-mash of information in the "Notes on using __slots__ section") - I intend to move some of that information into the exposition/introduction.

I have also been reviewing my changes and actively working on it with a volunteer at the PyCon sprints, Joshua Goldin. Will submit a pull request soon, tonight or tomorrow morning.