Rated 5 out of 5 stars

Since I already reviewed this add-on as very-very useful, I would like to share that there are some scripts along with "Stylish" add-on that can complement this add-on.

In order to hide the contacts list completely and show on mouse-over:

Just to show the images of the contacts (and also show on mouse-over):
(and yes, this is by me)

This review is for a previous version of the add-on (38.4).  This user has a previous review of this add-on.