This upgrade has three main areas of focus:
- Support for the new in content preferences
- Remove the need for the distribution directory (except in the case of disabling safe mode)
- Support for new Firefox 38 features (not done yet).
Removing support for the distribution directory was a major internal change, so I would appreciate any testing you can do.
My plan is to finish support for a few Firefox 38 specific features and then release next week.