The purpose of this extension-managing extension is simple: to give more control over plug-ins to the user. It does just that, but it does it in such a useful and comprehensive way that it's hard to imagine managing Firefox extensions without it. The best tool this application gives the user is a Restart Firefox button that restarts the browser quickly and re-opens all the tabs that were closed. It also checks for updates and can override the MaxVersionNumber of many older extensions that haven't been updated for version 3.
Users are given control of nearly everything concerning plug-ins, from the folder the plug-ins are saved in to context-menu choices to more complex hacks. The interface is laid out in a basic panel, and it's a bit overwhelming given all the choices it offers. Still, if you download only one extension, make it this one; then all the others you get will be far easier to handle.