Had Microsoft introduced the Explorer Mouse two years ago, we might have shrugged. At that point, optical and laser mice were more than sufficient for desktop PC users, even gamers. Now that many people have more than one computer, at least one of which typically a laptop, a mouse with a new sensor that works on more surfaces suddenly seems relevant. For roughly $70, Microsoft's Explorer Mouse will give you that flexibility, by virtue of its proprietary BlueTrack sensor. You can find more fully-featured mice for your desktop, but none that work as well on the living room carpet.
The Explorer Mouse is one of two products released this year from Microsoft using an internally developed sensor technology called BlueTrack. Marrying the accuracy of laser mice with the wide-area projection of optical mice, BlueTrack gives you the ability to use the Explorer Mouse on the reflective and rough-textured surfaces that would give other kinds of mice trouble.
While your current desktop mouse likely works just fine, we'd also bet you use it on some kind of surface suited to the task. A mouse pad or a desk blotter will pose no trouble to current mouse technologies. The trouble comes when you use your computer in a nonstandard location, a reflective kitchen countertop, for example, or on your lap in the living room. These surfaces can give optical and laser mice difficulty.