I think the introduction is not necessary and can be removed altogether:
"If you’re used to developing in a desktop environment, or on a mobile environment without thinking much about accessibility, you’ve come to the right place to learn about making mobile devices accessible. First, some essential background."
Agree with Norah about the intro.
Other workflow related issues include:
Mini personas might be more effective if integrated. If each was placed in context of the problem being addressed to help developers immediately connect the problem to a personal experience.
Topic info is generally well presented, and examples are good - some wording suggestions offered later in context
"Related Tips and Techniques" adds unneeded verbiage to the table of contents.
I think the introduction is not necessary and can be removed altogether: "If you’re used to developing in a desktop environment, or on a mobile environment without thinking much about accessibility, you’ve come to the right place to learn about making mobile devices accessible. First, some essential background."