Mozilla Thunderbird 0.7 has just been released. Go get it (or go to the Thunderbird 0.7 release FTP directory for the zip build).

New and noteworthy is the inclusion of the extension and theme managers (derived from that in Firefox). This is also a static build so performance has significantly improved.

Update: just saw this Promoting Mozilla Thunderbird page pointed to on one of the TrackBack pings I received. Nice buttons.