[ame=http://www.youtube.com/watch?v=HgiGd53jg2U]YouTube - Apple Magic Mouse (Video Presentation)[/ame]
video via Apple
"The entire mouse is a button."
As forecast by alert bloggers reading Apple's patent applications, the new mouse has multi-touch input over the entire top surface. A contextual menu can be brought up by tapping the upper left-hand corner, and this is user-configurable so that lefties can use the upper-right corner.
You can scroll vertically with a forward-back movement of your finger, and horizontally when you drag side to side. Keeping your finger on the surface allows precise control, while swiping causes the movement to continue with the momentum of your movement. The surface also supports free movement in both X and Y axes by scrolling in circles on the top of the mouse. This will take some getting used to, but I have a feeling I'll end up wondering how I got by without it. Swiping with two fingers, on the other hand, sends a "previous" or "next" command. This will allow you to skip tracks in iTunes, for example, or turn pages. Holding down the control key while scrolling allows you to zoom your screen: an up-scroll to zoom in and a down-scroll to zoom out.
Functions of the Magic Mouse are customizable in System Preferences, including the option to just turn off the multi-touch features.