We're getting very, very close to Thunderbird 1.0. Last night we took the last of the planned changes and if all tests out well today, we'll have a 1.0 Release Candidate tomorrow.
If you're available to help us test these candidate builds before they go out to hundreds of thousands of users (hopefully tomorrow) please join us today on IRC, server irc.mozilla.org, channel #mozillazine, for BugDay focused on Thunderbird testing and bug triage.