Rated 4 out of 5 stars

Very nice Add-on, thanks!

Suggestions...
1. Instead of 2 preset sizes, let users select their own size.
2. I mainly got NewScrollbars because it allows for a dark background. But I'm sure other users would like to select any color they wished for the background.
3. A few styles to choose from would be nice. And if possible, allow users to add their own design to the style.

This review is for a previous version of the add-on (1.0.4). 

Thanks.

1. The two present sizes will remain for the predefined scrollbars but there will be more settings in v1.0.5 where one of them will be the custom size selection.
2. Colorpickers for scrollbars background, thumbs and buttons will be added to next release.
3. Maybe in a future release I could add some more styles. Atm a "style" (for e.g. predefined scrollbars) consists of 11 images. I simplyfied this in v1.0.5 so there are only three images needed now. Unfortunately the scrollbar caps got removed for this kind of simplification.