Thunderbird 5 Rated 5 out of 5 stars

I would like to second Grzegorz_P: this is an excellent add-on and I came to love it during my 3.1; however, I started using the new version quite early as it is reasonably stable and with the conversations and compose add-ons it looks like a completely new generation email client - but it is badly missing a tab which I can have open all the time with my address book(s).

This review is for a previous version of the add-on (1.4.1). 

Done. A week that I've tested and modified it for TB5... just forget to put it on AMO.