Rated 1 out of 5 stars

The user agent is a trivial to change setting (via general.useragent.override). The whole point of having an extension, for me, would be to conveniently "bookmark" a bunch of user agents, while keeping a similar behavior as with general.useragent.override, ie once you set it, you keep it until you change it back.
Unfortunately, every time you restart the browser, the extension switches back to the default user agent. Spoofing failed....