Very awkward to use. It can't be activated for the current Page/site, but, instead, its address must be manually added to the list of the desired agent string, what is possibly the worst way to implement it (what if a site matches more than one list, the first string is selected or does it randomise amongst all matches?) I also had problems using * as a wildcard, forcing me to use full URL.

This add-on functions as the name says.

Gripes: The add-on is not suited for small screens, especially on Android, as some of the Android phones' smallest screen resolutions are only 240x320px in size.

It's not work on Firefox for Android

Cannot export/import user agent list from old "User Agent Switcher" add-on.
Cannot wipe out all existing user agents with a single click
UI looks confusing, far less comfortable than aforementioned add-on

Three stars because it does the job, but I'm still looking for a more user-friendly option.