In a total splurge, I got a Wacom Bamboo 6 x 8 graphics tablet.
It’s wonderful, and I wish I were artist enough to use it properly.
Unfortunately, last time I updated Ubuntu, it quit working. I had hoped that the upgrade to 8.10 would fix that, and it did — almost.
The stylus on this thing has an “eraser” button, which can be set in the GIMP to work just like an eraser. There’s also a wireless mouse that works with the tablet.
The stylus works, pressure sensitive, side buttons, and all, but neither the mouse nor the eraser work. I just spent a couple of hours dinking with /etc/x11/xorg.conf, which controls the user interface, but no joy.
So here’s my current mood:

self-doodle
Look, on a good day? I can pick out “Chopsticks” on a cheap toy piano. Controlling the GIMP with the Bamboo is like putting me in front of a really big pipe organ. I can pick out “Chopsticks” on any number of interesting-sounding stops.
Strongly, strongly recommended for anyone with any interest in drawing on the computer. Far easier to use than a mouse (fingers instead of wrist), pressure sensitive strokes — fabulous. I hope to be worthy.
One purchasing choice to consider: I went for the 6″ x 8″ pad. This gives you extra resolution. However, the cursor position on the screen is controlled by the absolute position of the stylus on the pad. To go from one side of the screen to the other, you must move the stylus from one side of the pad to the other. You cannot do this with simply wrist action; you must move your whole forearm. Also, with an ordinary mouse, if something on the desk gets in your way, you pick up the mouse, move it back a bit, and put it down. This trick does not work with the Bamboo. These problems would be less severe with the smaller 4″ x 6″ pad. Moreover, the small pad comes in a stripped down package with no mouse and no software — $70 versus $200 for the 6×8 Bamboo “Fun” package I got.
I think I prefer the larger version, but it’s definitely taking some getting used to.
[update]
I believe that ergonomically, the pen position, with your wrist held sideways, is far superior to the flat wrist mouse position. It’s the difference between a good handgun stance and the gangsta grip.