Microsoft Arc Mouse (black)

Pros: Very cool shape that is elegant and makes you think "why aren't all notebook mice like this?" Unfolded it reminds me of those bad-ass rolling/shooting force-field droids in Star Wars...

Cons: It's not as accurate as other modern top of the line mice. The wheel doesn't always register a movement. The working ergonomics are poor.

Summary: I expected better performance from the mouse itself (poor point & scroll accuracy) this isn't a cheap mouse, I expected better precision. I also expected much better ergonomics when actually using the mouse. Your thumb and pinky have no place to rest when using this mouse. On a normal mouse when I'm making broad movements my thumb and pinky are resting on the side of the mouse, when I'm doing very precise movements they're touching the desk and dampening/controlling the mouse movement. You can't do either of those things with the arc mouse.