Well, for my sins I have become a Thunderbird 3.0a1 user, and I can't say I'm happy. Several times the program has threatened to update itself, and eventually the promised (threatened?) upgrade arrived. [NOTE: apparently the 3-series builds are intended only for developers].
The error that originally caused me to update to the latest version is even worse in 3.0a1. Message contents are now being mangled on a regular basis. I have no idea whether they can be recovered correctly or not, and I am beginniing to lose confidence in what has until now been a reasonably reliable piece of software. It's ironic that I am suffering this problem even worse than I was because I wanted to help the project by making an accurate bug report.
If many other users are suffering the same problems I am then this issue needs to be addressed before it starts to give open source a bad name.