For those who want more screen space, Thunderbird 9 (scheduled for release on December 20th) will give you the ability on Windows to hide the Menu Bar (File, Edit, View) like you can now in Firefox. Just like in Firefox, you can press the ALT key or F10 to temporarily display the Menu Bar. To permanently restore, press ALT then go to View > Toolbars > Menu Bar. Alternatively, if you still have the Mail Toolbar enabled, you can right-click and select Menu Bar as well.
If you want to try to Thunderbird 9 Earlybird or 8 Beta,they can be obtained here.