The Wacom driver (xf86Wacom.c.gz) included in the xfree ebuild is completely outdated and doesn't support the currently available tablets (Volito, Intuos2 USB, Graphire 3, Cintiq). There's an updated, very stable driver by the LinuxWacom project (http://linuxwacom.sourceforge.net/), but it's very hard to compile it, and the prebuilt binary by LinuxWacom only supports x86, not AMD64 nor anything else. I'll attach the updated driver. (0.4.1 stable - don't use 0.5.4 yet!)
Created attachment 23237 [details] Wacom xfree driver v0.4.1
Bryan, want to look into building this against SDK? <spyderous> can you look at building http://linuxwacom.sourceforge.net/index.php/howto/builddrv against the SDK <spyderous> the wacom driver <spyderous> especially the comment in the conclusion
Alright, linuxwacom-0.6.0 stable is out, and the included drivers still doesn't work...
Ok, I've got an ebuild awaiting testing and some polishing on my laptop, which I will try to do tonight. Thing is, it builds against the SDK (as Donnie requested above), so it will need to wait for the next version of xfree, which will have a patch merging some headers needed for it into the SDK.
Fixed in 4.3.0-r6. USE=sdk with xfree, then emerge linuxwacom.