Technologically speaking, the desktop mouse is fairly ancient--it turns 41 this year, making it older than the personal computer.
Unlike most other computer-related tools, it hasn't changed much in that time. Most of the innovations in tracking, ergonomics, and cordless technology were developed years ago, and merely refined ever since. In my mind, the Logitech Cordless Mouseman Optical represents the end of the mouse's current evolution, at least until the next major conceptual leap forward.
Consider the evidence. The radio technology used for cordless mice has remained essentially unchanged since its inception ten years ago; the basic recessed thumb rest/button and arched design have been around for some time as well. It can even be argued that the relatively recent works-on-any-surface optical technology, popularized by Microsoft's IntelliMouse series, is based on the original optical mouse designed twenty years ago. There's really nowhere else to go with these except for greater precision.
Even if it is an evolutionary dead end, the ultra-chic Cordless Mouseman Optical is a great way to go out. As its name implies, it combines cordless technology with the latest and greatest in optical technology, along with Logitech's typical stellar design. It fairly glides over the desktop (or pants leg, or CD jewel case, or whatever's handy) without a pesky rubber ball slowing it down. So much so, you may want to crank your mouse pointer speed settings down a few notches. It takes a little while to get used to near-frictionless mousing, but the end result is worth it.