This mouse is designed to pair well with Microsoft's Natural Ergonomic Keyboard 4000, which is one of the most comfortable keyboards I've ever used. The Natural 6000 mouse has an unusual rounded shape, resembling a softball. There have been other "extremely ergonomic" mice before, but were so strange-looking (no matter how well they performed) that they remain a niche item for ergonomic extremists.
The wireless interface is the same 27MHz technology Microsoft has been using for years on their wireless mice. This technology has been improved over the past several years to reduce lag to the point that it is just as good as a wired mouse (when first introduced it was horribly laggy). The wireless receiver (which also ironically looks like a mouse) plugs directly into your PC's USB port, and has a range of about six feet. Although the low frequency is more prone to interferance and range issues, it should also, in theory, increase battery life.