I have finally had the time to release a new version of the User Agent Switcher extension. The main changes in this release are the support for folders and separators in the user agent list as well as indicating a non-default user agent has been selected by more than just the icon color. The user agent list has also been updated to include both the Googlebot and the iPhone user agents.
A full set of release notes is available.

Hello,
Il like this extension to easy change UA.
Is it possible to develop a new fonction to randomly change the User Agent for a better privacy ?
I know that some websites are looking at our UserAgent to recognise us. With that random user agent, we become anonymous even if we change our IP.
Maybe i can help, bye.
Random user agents have been requested before and I currently have no plans to add this feature to the extension.
Ok, happy to see that more people want that.
Could be great if you plan that. Maybe it can be done on every Firefox reload.