I am not sure why I never heard about this extension before now but it is very interesting.
This extension adds a few extras useful to those that regularly test nightly builds of Firefox, Thunderbird and the Application Suite.
This extension now works on branch builds of Firefox and Thunderbird.
* Allows you to install incompatible extensions (experimental).
* Allows you to force the application to believe an extension is compatible with the current version and enable it. (Only works on recent builds of Firefox and Thunderbird, branch and trunk since 20/08/2005).
* Adds a menu item to let you to copy the build identifier to the clipboard.
* Adds a menu item to let you insert the build identifier into the current text box.
* Adds a toolbar button to let you insert the build identifier into the current text box (Not supported in the Application Suite).
* Provides an easy way to launch talkback.
* Lets you customise the title bar to include the build identifier and other information.