While you're waiting for a reply, you may want to try emailing Aspyr and Wacom tech support. Also, since you've already checked for Doom 3 updates, maybe check for a driver update from Wacom?
FWIW, I originally used a Logitech MX310 mouse when I bought Doom 3 back in May. But I recently bought a dual 2.5Ghz G5 Tower and have been using the single button Apple Pro mouse with Doom 3. It's been working great so far. But that's probably becasue Doom 3 isn't as fast paced as Quake 3 or similar FPS games. You usually have more time to set up for different areas (long range/short range) and monsters (effective weapons) than in most FPS games. Well, at least in the earlier part of the game

Later on things get quite intense. Even so, I just got out of hell, killed the guardian, and rescued the soul cube using the pro mouse. Damn, this game looks and plays incredible when you've got a G5
