I don't think the support for the CTH670 is in the Fedora kernel yet. It's being put into the 3.3 kernel, and I'm not certain if Fedora has backported it yet (or if they are going to). (It wasn't put in until the middle to end of Oct)
Even then, I don't think all features of the CTH670 are fully supported yet, even in the 3.3 kernel module. I remember seeing something about the multifinger touch gesture stuff not being implemented for that model yet, but I could be wrong.
I have the CTH460 and just like Pete, mine has worked with Fedora since F15, but prior to that, I had to pull the linuxwacom drivers and build my own kernel module. I posted on here several places how to do that. It's not hard, just a PITA to keep up with rebuilding it every time you get a kernel update.
I haven't had any issues at all with mine and gimp, though. I just set it up in the extended input devices in gimp, and it work fine in both absolute and relative mode, although I prefer absolute mode.
I do like those nice scripts that Pete put up there to change the config, though.. I do believe they have been swiped