I have an Apple Magic Mouse and it seems like ever since upgrading to Parallels 9 (with the latest patches) the "mouse wheel" scrolling in Windows 8 has been very jumpy and inconsistent. It some apps like Visio the scrolling is a little too fast. In other apps like Visual Studio it's too slow. In the mouse control panel in Windows there appears to be little I can do to change the behavior. There is only a setting to adjust how many "lines" one "notch" on the scroll wheel will move the screen... but of course the Magic Mouse has no notches and on many screens there are no "lines".