With most of the attention on the Google Chrome browser release for OSX and Linux, the release of Thunderbird 3 got overshadowed. While some feel that stand-alone email readers are becoming obsolete, I still believe that a dedicate email client is very useful especially for power users. That said, the convenience and advancements of browser-based email such as GMail have come such a long way that we're not far from the time (if we're not already there) when email clients compliments the web version rather then the other way around.
Upgrading from TB2 to TB3 was painless. Just install the application and it handled all the upgrades. It asks whether you want to switch to using some of the new interface features or stick with the previous ones and then it will start to create the search index for all your email. Search was definitely one of the weaknesses of previous TBs especially when you compare it to Gmail's search, but that seems to be one of the areas that TB3 really tries to improve on in this release. I think TB3 also took the right steps in keeping itself relevant by integrating better with web-based mail system. The one shortcoming is that it still doesn't integrate directly with online contacts that you might have with Yahoo or Google. TB3's interface is also a little more Firefox-like. Desktop clients have some advantages of running on the OS so I still feel that they should continue to use that advantage. It isn't a radical change, though, so it might be that good balance between the bringing users some familiarity with browsers while still exposing email features.
I need to play with it more but so far I tip my hat to the team for this nice release.