Add-on Compatibility Reporter :: Add-ons for Firefox
This add-on for Firefox is the missing link if you're using alpha or beta builds of the browser. With this little thing your addons will be enabled although they are not yet updated to work with the latest version of the browser. You have an opportunity to report whether the addons still work or not with the latest build. Now I can again install all the addons I'm used to. Firefox will happily allow you to install extensions that would not install because of incompatibility.