Rated 3 out of 5 stars

It is a great addon, because you can start FF and Thunderbird minimized. Yet, there remain two problem: In Ubuntu-Distros Thunderbird won't start minimized. And in ubuntu karmic, it makes firefox 3.5 crash. For those interested, here I filed a bug:
Here is the link: https://bugs.launchpad.net/ubuntu/+source/firefox-3.5/+bug/475188

This review is for a previous version of the add-on (0.2.3).