> I'm not saying that you wouldn't be able to do this with a web-based mail client.

In fact, using gmail should take fewer strokes than that. Assuming you have a keyboard shortcut to spawn a gmail window, enter will take you to the first message, and 'e' will archive that message. Command-Q/Alt-F4 to quit.

Labels can be applied with an 'l' and the label name, next/last message is 'n'/'p'.

The full list of keyboard shortcuts is available here: https://mail.google.com/support/bin/answer.py?answer=6594

It would, of course, be better if they let you customize the shortcuts and sped up the loading of the initial page.