Review for User Agent Switcher by Raul Agrait
Rated 4 out of 5 stars
To all those having problems finding the options in FF4: To see the User Agent Switcher options again, you just have to turn on the Menu Bar, which is turned off by default in Firefox 4.
Firefox Button In Top Left --> Options --> Menu Bar
To create your own collections, you must have a Mozilla Add-ons account.