MagicPrefs was designed to improve the overall functionality of the Magic Mouse. While many people have eschewed the Magic Mouse for the Apple Trackpad, there are users who still prefer having a mouse around. Using the gestures comes with a learning curve, but once you know them, they become somewhat intuitive. Tracking speed can be augmented by up to 200%. The overall touch surface of the Magic Mouse is quite smaller than the Apple Trackpad, and in my opinion, the Trackpad is the better buy, especially when combined with something like Better Touch Tool.
JiTouch was improved by adding more support for the Magic Mouse. In the latest version, you can access fully customizable actions, gestures, flicking quickly between Spaces in OS X, and tab switching. Unlike BTT and MagicPrefs, JiTouch isn't free but costs $5.99.
MouseWizard allows you to give your MagicMouse up to six extra buttons. It also supports 'pinch', 'bloat', and 'tap to click' trackpad gestures, as well as some special gestures like 'coverup', which will make your Mac go to sleep. This is simple app to setup and allows users to access good features without having to bother with advanced features. It costs $5.