Rated 4 out of 5 stars

The beta works well enough that you might as well get it up here. You can list it as a beta, so that only people with Firefox 4 will get it. (Stylish does this.)

The only problem I have with it is that it assumes that the tabs are on bottom. When they are on top, you don't need that extra band of color (unless you can always make it below the tabs.)

This review is for a previous version of the add-on (4.6.5).