Please check out the builds for your locale if you have the chance. We're particularly looking for folks who use POP to fetch their mail to give these builds a good once-over. That said, we'd very much appreciate all the testing help we can get.
If you do find bugs while testing, please mark them as blocking bug 489128. Thanks!
Assuming no show-stoppers are found, we hope to be able to release Thunderbird 3.0 beta3 on Tuesday, July 21st.