Since Firefox moved to a rapid release cycle, there has been concern by some (including myself) as to whether add-ons would stay compatible with each of the new versions, and how one would go about testing to find any breaking changes. In news that makes a geek happy - Mozilla has taken care of that for me as I received notice from Mozilla that stated:
Dear add-on author,
Good news! Our automated tests did not detect any compatibility issues with your add-on Google Music Hotkeys and Firefox 9.*. We've updated your add-on's compatibility to work with Firefox 9.* so that our Aurora users can begin using it.
This compatibility bump is server-side and we did not modify your add-on package in any way. If you wish or need to revert this change, just go to your add-on edit page on addons.mozilla.org, select the Status & Versions page, then the version, and change its maxVersion compatibility back to its previous value.
For more information on our new compatibility process with rapid Firefox releases, please read this post: http://blog.mozilla.com/