It would be Nice Rated 4 out of 5 stars
If it works with your setup, it's great. For a visual person, it is a way to separate the tabs. It would be nice if you could select your own color, but after a while you remember which are which.
The big BUT is, it does not work with many tab add ons. Using 188.8.131.52, Tab Mix Plus, Send URLS, and Tab IE, no theme, it does not work. So for me, its off the list.