It took us a few minutes to realize what Microsoft's new Arc Mouse is all about. The collapsible design at first suggested that it's both a full-size mouse and a notebook mouse in one product. We were confused as to who would want such a thing. Upon playing with it, we realized that there's actually some smarter design going on here. The unique shape and button layout does present some usability issues, but overall, the $60 Arc Mouse may be the best solution for those looking for a full-size, travel-friendly mouse.
The benefit of the Arc Mouse is not that it works as a "notebook mouse" when you fold it in half. Indeed, the power to the mouse cuts out when it's folded, so it won't work in that mode at all. Instead, folding the Arc Mouse makes it more generally travel-friendly. First, it reduces the size of the device, cutting its length by more than a third. But there's also a small, magnetic cradle on the underside of the tail portion that folds in, to hold the mouse's thumbnail-size USB receiver. When the mouse is collapsed, the tail portion secures the receiver, ensuring that you'll have all of the necessary pieces together when you take the mouse out of your bag.