Simple yet great add-on. Works perfectly well.
I mostly use Ctrl-W key shortcut or this add-on to close current page because I find reaching with my mouse to the active tab inconvenient. With this add-on the close button location is always where I expect it to be, and the button is easy to reach, so I don't have to look and find which tab is active and don't have to move my mouse all the way up there.