To get a Wacom Graphics Tablet to work, you will first need to make sure that you have the correct modules in your kernel.

*** Kernel Configuration ***

In the "Input Device Support" Section
Code:
(1600) Horizontal screen resolution
(1200) Vertical screen resolution
(M) Event interface
I modularize evdev but you can compile it right in if you want to. Obviously your screen resolution settings may be different than mine depending on what screen resolution you run at.

In the USB Section
Code:
(*)   USB Human Interface Device (full HID) support
(*) HID input layer support
(*) Wacom Intuos/Graphire tablet support
I just compile them right it, you can modularize them if you want to.

Recompile your kernel if needed, if not then continue on.

*** Loading the modules ***

Next, you need to have your system load evdev on boot. With Gentoo, you would add evdev to /etc/modules.autoload.d/. Other distros have similar mechanisms, please refer to your documentation. [if you modularized any other of the modules, you may need to load them this way as well]

*** Modifying XF86Config ***

Lastly, you will need to add the appropriate lines to your /etc/X11/XF86Config file.

Add the following Input Devices
Code:
Section "InputDevice"

        Identifier      "stylus"                # Wacom Graphics Tablet
        Driver          "wacom"
        Option          "Type"                  "stylus"
        Option          "Device"                "/dev/input/event0"
        Option          "Mode"                  "absolute"
        Option          "USB"                   "on"
        Option          "Speed"                 "3.0"
        Option          "Threshold"             "10"

EndSection


Section "InputDevice"

        Identifier      "eraser"                # Wacom Graphicvs TAblet
        Driver          "wacom"
        Option          "Type"                  "eraser"
        Option          "Device"                "/dev/input/event0"
        Option          "Mode"                  "absolute"
        Option          "USB"                   "on"
        Option          "Tilt"                  "on"
#       Option          "TiltInvert"            "on"
        Option          "Threshold"             "10"

EndSection


Section "InputDevice"

        Identifier      "cursor"                # Wacom Graphics Tablet
        Driver          "wacom"
        Option          "Type"                  "cursor"
        Option          "Device"                "/dev/input/event0"
        Option          "Mode"                  "absolute"
        Option          "USB"                   "on"
        Option          "Tilt"                  "on"
#       Option          "TiltInvert"            "on"
        Option          "Threshold"             "10"

EndSection
Add the following to the "ServerLayout Section"
Code:
        InputDevice     "stylus"                        "AlwaysCore"
        InputDevice     "eraser"                        "AlwaysCore"
        InputDevice     "cursor"                        "AlwaysCore"
Reboot if you had to compile a new kernel, or just load the modules and restart X if you already had all the required ones.

If you did everything correctly, then the Gimp will pick it up atuomatically.

You can check the devices in the Devices dialog in File | Dialogs in the Gimp. 1.2.x and the upcomojng 2.x have slightly different dialogs but they both support this device. You assign pointers to the different devices i.e. eraser, stylus, etc.