Great addon. With a widescreen monitor there's a lot of space that could be doing something more useful.

One feature that I'd like to see, in tabs generally but it makes particular sense here, is a way of intelligently abbreviating the title text. For example on the Safari books site the titles all start with 'Safari Books Online' before getting to the part I'm interested in: the book's title. I'd like to see an addon that factored out repeated text in tab titles, or focused in on the part that's different.