Awesome simple extension. I've been using this religiously for the "Close all right tabs" shortcut. I binded it to "Alt+Shift+R". I've since moved to Zen, unfortunately this extension doesn't have a "Close all tabs below" shortcut.

Edit: Nevermind guys, it still works on Zen for the "Close all right tabs" shortcut! Sometimes the shortcut doesn't register because my tab doesn't get focused properly.