GTX 680 Mac Edition ROM woes continue.
Aside from the aforementioned display bugs in the Mac version of Photoshop (that also affects 9 series cards), graphics performance in apps such as Photoshop or Blender also take a dive under Windows. I tested in Bootcamp and a real PC. Gaming is unaffected, the issues are occurring in windowed applications only.
It appears that lately Nvidia has been releasing drivers on Windows and OS X that are not thoroughly tested with Mac EFI ROMs. This is probably a sign that their Mac development department has shrunk down to just a handful of part timers who do some work on Metal support and push out a new version of the web driver (with no noticeable core changes) whenever there is an OS X update.