Indeed as others have mentioned, useless IMO. Try 'Organize Search Engines' ( https://addons.mozilla.org/en-US/firefox/addon/organize-search-engines/ ), a papa add-on but alive and still efficient (FF 3.6 and above) !
Kind of pointless extension. Can not order search engines. Can not set any options. At least if it was possible to set Google/Bing/Wikipedia autosuggest feature for some of search engines, I would say this extension brings something new to marketplace.
It would be way better if 1. it showed the urls in the description. 2. it did respect the order in which all search plugins are shown in the search bar. I have them sorted and your extension lists them alphabetically. 3. it would be possible to change their order by drag-n-drop. 4. it showed keywords set for search-engines. 5. the keywords would be editable. 6. the menu "Search Engines" in AOM would have an icon, like other menus do. 7. it gets unpacked when being installed, so instead of having a single *.xpi file you have many small ones, which cause more disk I/O (so it dies faster) + it's even a bit slower.