@urlwolf: How do you like the Filco touchpad?
I have a Ergonomic Touchpad for my PC, but it's never felt quite right (lacking multi finger gestures, sensitivity, etc.).
I do use Autohotkey/Mouse Keys to map Caps Lock, Insert, Keypad Enter, and Keypad 5 to be left mouse button on my PC, but I wish there was an equivalent (besides Mouse Keys) to do the same on my Mac.
@ripster: Another consideration is the lever material. The buttons on my Kensington Expert is too flexible (cheap?) to give me any significant leverage.