Now, this is AWESOME!
I just noticed Gmail Labs show up in my Gmail settings. So, I clicked through and turned on a new lab feature called Mouse Gestures. Basically, by pressing your pen button or mouse right button you can navigate through your emails: right to go to the next conversation, left to the previous conversation, and up to go back to the inbox view. It works awesome on a Tablet PC, and is quite nifty for use while in slate mode.
To use with your pen and Tablet PC, make sure your button set to be used a right mouse click. See the Pen and Input Devices section in the Control Panel.
If you don’t have Gmail Labs active yet, be patient. It should be there soon.