Apple's Magic Mouse is two years old. It attempted to merge two interfaces—touch and mousing—in a meaningful way by hybridizing a capacitive touch surface and a mouse. It's pretty good. Microsoft's Touch Mouse is like that, but for Windows 7. And actually designed for human hands to hold it.
Well, the ergonomics. It's why Microsoft hardware is renowned. They make comfortable stuff. I typically dislike ambidextrous mice. Not this one. Also, the Touch Mouse's custom software delivers a true Expose-type feature to Windows 7 that reveals all over your open windows with a swooshy animation. It's so good it should just be built into Windows 7 by default, really.
Oh, how to put this delicately: It doesn't work? One-finger scrolling is kind of like spinning The Big Wheel on the Price Is Right—you never know where it's going to stop. The back and forward thumb gestures are truly awkward, and only work about half the time. It misinterprets touches, often, and with a vengeance. But the real killer? Right-click only works about 60-70 percent of the time. And because I could never trust the mouse to do what I needed it to, I never felt super comfortable holding it, since I was always paranoid I'd set off a horrible chain reaction of gestures that would like restart the sun or something.
Not unless there's a mega firmware update that magically makes it awesome. The prototype I saw over a year ago had tons of promise, and it could be killer mouse, even at $60. If, you know, it worked.