Pros: 1. Permits configuration of extra buttons on legacy mice. These buttons are unusable otherwise.
2. Enables you to assign a set of keystrokes to a button.
3. "Make scroll wheel scroll window under cursor" (i.e. scrolling in a non-focused window) works flawlessly (Win7 x64). I've had problems with KatMouse and AlwaysMouseWheel.
Other Thoughts: None