We’ve started landing patches for the next 2.0.0.x release of Thunderbird, as we get the patches approved by the 2.0.0.x driver team. This means that having people running the latest 1.8 nightly builds is very helpful for us, to make sure the fixes work, and there aren’t any regressions. You can find the latest 1.8/2.0.0.x builds here:
ftp://ftp.mozilla.org/pub/mozilla.org/thunderbird/nightly/latest-mozilla1.8
The Rumbling Edge should start tracking the bugs that are fixed in the 2.0.0.5 pre builds soon.