Rated 5 out of 5 stars

This is an excellent add-on Aris well done.

The only thing i would like to see this add-on include would be a Transparency slider and this would be absolutely perfect.

This review is for a previous version of the add-on (1.0.7). 

Thanks.

Level of trancparency can be set in Windows settings or do you mean with "slider" scrollbars? If so there is my extension called "NewScrollbars" ( https://addons.mozilla.org/addon/noiascrollbars/versions/ ) where you can set a semitransparent default scrollbar in version 1.0.3pre4+.