Sadly, I have a crippled thumb and can't use trackballs all that well, though that marble trackball looks interesting...
Maybe I could convince the Office Max to let me test drive one.
It would have to be wireless, though.
On a side note, why the hell don't they make more BT mice? I just really don't like having to deprive myself of a USB port on my laptop on a semipermanent basis just for a mouse.