Thunderbird for Linux is getting some nice visual changes as Andreas Nilsson shows off some teaser screenshots of Thunderbird looking great on Linux Systems. Work is being done on bringing better integration with GTK themes, very similar to visual improvements that landed in Firefox 4 earlier.
This is work in progress and changes are yet to land. Thunderbird is proposed to be the default email client in Ubuntu 11.10 Oneiric Ocelot.
via Random Pixels