Author here, just saw this pop up.

The engine isn't really in a released state yet and doesn't have a numbered released yet (darn lack of docs), but it's been used internally for a number of projects, most recently:

http://www.html5gamedevelopment.org/StateofHTML5GameDevelopm...

A rewrite of a couple of the parts (particularly scenes and some UI components) is a work-in-progress.

The primary goal of the engine is to be a small, modular, very JavaScript-like and to have a full test suite for the core parts of the system - http://html5quintus.com/quintus/specs/SpecRunner.html (this will help verify cross-browser behavior)

Forgot to add, this Engine came out of a book I wrote, and the examples for that book all run on Mobile: http://mh5gd.com/