Logitech has been pumping up their V400 wireless mouse for quite some time now, nearly going so far as to claim that it will do your homework and wash your car. By far, the most hyped feature is its so-called dual laser engine, which is supposed to improve upon regular laser mice that take snapshots of the surface to determine its location. Rather than doing that, the dual lasers actually detect differences in the frequencies of light, supposedly making for a more accurate mouse experience. For the most part, that works as advertised, although there were incidents where it didn't track particularly well, such as on a light carpet.
Otherwise, the mouse is your standard wireless mouse with plenty of buttons bells and whistles (such as side scrolling, button remapping, etc.). It's fairly comfortable, and battery life is most impressive. So if you're in the market for a decent, fairly advanced and nicely priced (around $40) mouse, the Logitech V400 just might be the ticket, just don't expect groundbreaking performance from the dual lasers.
Logitech V400 Cordless Notebook Mouse [Everything USB]