I am no real UI designer as those awesome folks above are, so the simple video I produced below is nowhere as elaborate as their mockups.
“Gristmill In Action”: (click here or the image to see the full resolution video)
(Either left-click to load the .swf directly, or right-click the image and click “Save Link As” to save the 6.9MB file to your disk)
A sample .xpi, current as of 12 Aug 08, is available, and works for release builds as well. Many thanks ought to go to the folks who have been developing Gristmill, including but not limited to Clint Talbert and Mikael Rogers. It must be noted that Gristmill is still in heavy development though.
Done up using Jing, a free screencast application.
P.S.: Gristmill does not yet work for Thunderbird or Lightning / Sunbird, though it is theoretically possible. It will be awesome if someone can get it to work for those apps.
Edit: Clint just told me that Martin Schroeder has just gotten Gristmill to work on Thunderbird _and_ Sunbird. Way to go, Martin!