Works well. I have one site where I need webRTC so this addon works well to keep it turned off by default and let me turn it on quickly just for that site. I can just click the icon to turn it on for that one site, refresh the page to get it working, then click the icon again to disable it again for everything else (that site will continue to work even after i disable it again, as long as I don't refresh the page).

What firefox REALLY needs if it cares about privacy and security is for webRTC to have a whitelist mode where only sites you add to the whitelist will allow webRTC and it is disabled for everything else.