If USB Overdrive for MacOSX is installed, the scrolling speed is even faster if you move the wheel faster. This is also supported by iCab, but you may wish to set a lower scrolling speed in the iCab preferences in this case to make this feature work much better.
Mac OS X itself doesn't evaluate the speed when moving the mouse wheel, so without USB Overdrive installed you may wish to configure a higher scrolling speed in the iCab preferences.