The other day sister blog TUAW mentioned a series of interviews with Mac pundits and developers about Mail.app, OS X's default mail application. Leander Kahney found Mail would choke on tons of mail, and switched to Thunderbird. And I'll admit, Thunderbird is a fantastic app, despite certain hiccups (POP vs. IMAP comes to mind). With calendar integration, and hopefully later other features, Thunderbird will probably eventually replace my own mail tools. But for now, Thunderbird is a bit of an acquired taste. Leo Notenboom tried switching from Outlook to Thunderbird. And then he switched back. Essentially Leo unearthed a bug that was a deal-breaker, and having only spent a couple of hours in Thunderbird, I wouldn't call this a fair test. Then again, any bug that forces a user to stop using an app is a fair test, but only for that user. Clearly Thunderbird isn't ready for prime time, but it's getting there...