As a desktop user of Firefox on Linux I found the two demos with the modified scrollbars subjectively worse than default. As a user I use the scroll bar to (1)

As a desktop user of Firefox on Linux I found the two demos with the modified scrollbars subjectively worse than default. As a user I use the scroll bar to (1) identify if a section can be scrolled, (2) identify where in the section I am with regards to the scroll height, and if needed (3) manually scroll by clicking on the scroll bar and dragging with the mouse. The two demos retain these three capabilities but for me make them more difficult and less efficient. I agree with what other users have said: please do not touch my scrollbars.