My guess is that I'm close very close to your ideal intended reader. I'm a javascript programmer looking for better ways to handle and persist state in my apps.

I think you might be dismissing the above criticism too quickly. Arriving at the page there wasn't much that told me what problems Backbone would solve or what features it offered. It was also rather difficult to actually get to a working version of the Todos demo (it's not linked from the annotated source or the step by step tutorial, as far as I can tell).

In the same way that there's a bolded summary of the idea being expressed at the start of each page of the tutorial, I think a similar summary of Backbone at the beginning of the tutorial would be helpful.

Yep, fixed (Todos link), and fixed (Backbone explanation)! :)

I went to the project home page and found the first paragraph in the intro section to be the most concise statement of the problem Backbone.js is trying to solve, but even that states the case for the project's existence in negative terms: it helps you avoid a problem. But that problem comes up when you're trying to accomplish something, and it would be better to say that Backbone.js is an awesome way to insert MVC stuff here.