At work I use an intuos4 (no screen on that yet). I love using the wheel control for brush size and canvas rotation.
I thought about getting a space navigator, which would also be useful for navigating in various other packages, but is fairly expensive for what it is. Than I came across this:Griffin Powermate
It's basically just a spinner knob and clickable button in one, USB and from the sound of it very programmable.
I thought someone might like to use it. It's about half the price of the navigator.