Doesn't work on click-test dot com.

Not great on Debian Linux 60.4.0esr (64-bit). Sometimes it works, sometimes it doesn't

The clicking speed is rather sluggish.

The clicking requires to hold the key, there's no toggle option.

The "Save" button is not enough after changing the key, the addon has to be deactivated and reactivated for the changes to apply.

It is not possible to indicate a input in a page to send clicks to it even on the background, it just simulates clicks under the mouse cursor.