Mice with an additional "wheel" between the left and right buttons are very useful, and scrolling with the wheel soon becomes second nature.
Unfortunately, very few applications support the wheel. Trying to use the wheel in an application that doesn't support it is very frustrating.
SmartWheel adds wheel scolling support to the majority of applications, including 16bit ones, even if they weren't originally designed with wheel support.
It also provides the rather neat "button free" proportional scrolling that some modern apps have. Click the wheel, then simply moving the mouse causes scrolling. The further you move the faster the scroll. Press any key or click on any mouse button to stop scrolling. Try it, you'll love it! This "button free scrolling" also works with three-button mice, using the middle button.