Rated 1 out of 5 stars

A stupid concept. The user agent should be switched to something that would ease access to some site and not to scream: I'm the one who runs a small screen device with a resolution of 2000x900 pixels

Extra: Reply to José Almeida
If and only IF the site does not do any other check. Also, there are about three addons with the exact same set of features, including working with the latest Firefox and without the need to restart. So I should add Pointless to the description.

This review is for a previous version of the add-on (0.2.2). 

Override User Agent does not improve your web experience, should be used only for testing web development

eg: select a mobile user agent as the android and access google.com, he will give you a different format for viewing, because google.com offers this

an example of real use: you created a website, but do not want to display the login field for bots, you create a code to hide this field based on the user agent, but how to test? Simple! With this addon :)

Thanks for review

For Extra Reply: Really there are others similar addons, the main difference of this addon is the location (toolbar / addon bar).
Before creating this addon I tried using the "userAgentUpdater" was very useful, but had conflicts with the "Menu Editor" and use the normal right click always show it (because of that I use "Menu Editor", clear the context menu)...
I also used the "User Agent RG" but it is hard to access (or not appropriate)...
And finally the famous "User Agent Switcher", full of options and everything, but often you do not need it all, just something easy and practical is enough and that's what I tried to do with this addon, did something to my need and have made available to others

Note: This addon also is restartless and compatible with firefox 11-14 (tested), can be compatible with future versions, if not I certainly be updating to make compatible with latest release