Just noticed it was released a few days ago. If you haven't tried it... it's free, quick, and pretty feature-rich. If you somehow see only v2.8 in the Android Market, you can download v3.0 via your phone's browser to your SD card and then install from there. Remember to enable the "Install Apps from Outside the Market" to install the download, and then revert back to downloading only Market apps after installation (it will prompt you usually).

Downloads - k9mail - Project Hosting on Google Code