Looks great and all, but why I would use HTML5stac rather than just backbone+bootstrap which would provide more control. Is there a particularly nice layer of abstraction that HTML5stac provides?
HTML5stac provides the complete backend, including the models and REST APIs to go with it. And it's full-stack JavaScript too, both on the client and server.
The demo app does in fact using Backbone+Bootstrap.
What HTML5stac makes dead simple for you is mapping your backend data models to Backbone Collections. In addition, we have responsive images, and adaptive templates, built into the framework.