I've been attempting to deploy HeadJS across numerous sites with the following plugins also installed:
1. Gigya or Janrain Engage
In both instances with the OpenStack services (Gigya, Janrain Engage) HeadJS can't seem to parse their JS scripts correctly, breaking third party authentication.
Also, WP-Minify has serious problems with HeadJS as HeadJS attempts to place all the minified JS data inside it, yet Minify expects it outside of the HeadJS loader functionality.