If anyone has a quadro 4000 could they test out sketchbook pro and a wacom tablet. I still haven't got any answers back from autodesk.
Have you considered checking out a GT120 before spending a lot of money on a card that's otherwise overkill? Because if Sketchbook Pro runs satisfying on your girlfriends macbook then Sketchbook is probably not pushing the GPU a lot anyway? Then all this is more about a bug and 1200$ is quite a hitch to work around a bug that might be fixed next week through an update?
I think people here still mix up sketchbook with sketchup. This is not a 3D app. I run Sketchbook with a GT120 (10.6 though) and it runs smoothly. I see no lag at all unless I have videos running on the other monitor that card is connected to. I do black & white sketching only though. Dunno what other more demanding apps you may be running, but if you do, you could dedicate a monitor to sketching with a GT120?