Nathan Alderman’s conclusion of Postbox 2:
If you’d like a top-notch upgrade to your e-mail experience at a reasonable price, and you can live without Exchange support, the terrific and thoughtful features built into Postbox definitely deserve your consideration.
Postbox is one of those apps that I want to love (another one is Pixelmator). I have tried Postbox many of times, including the 2.0 release after Chris Bowler posted about how much he loved it. I just can’t get into — I think I may be too stuck in my Mail.app ways.