Nice new tool! Rated 4 out of 5 stars

Very nice tool to assist developers and designers in creating accessible and usable web sites. I think the Errors, Features, and Alerts toolbar button represents the best quick check at functionality. I think the Structure/Order option could use some explanation text in the UI.
The text-only mode works as advertised.
For the Toggle Styles option it would be nice to have an indication what the two styles represent / how they change the application. Would it be possible to give the name of the style in the toolbar button when it is active?

This review is for a previous version of the add-on (0.9.4).