Simple, elegant, and does the job.
A few improvements I can think of:
Let us use the mouse wheel on the icon of the addon to increase/decrease speed.
Let us customize the keyboard shortcuts, or disable them completely.
These aren't must-haves, but would be nice.
Still, 5-star, and thank you.

There is a problem for those whose keyboards are not originally English and this causes that when you do PRESS SHIFT AND " . " OR SHIFT AND " , " then it reverses the speed and when you press CAPS LOCK TO MAKE IT BE IN English LETTERS then it does not allow you to use the keys at all and they do nothing. PLZ FIX IT PLZ