Call me bias, call me a jerk. Call me a biased jerk, but Microsoft mice suck horribly. Why some people prefer them I just won't ever understand. Several of friends I used to LAN with had an Intellimouse Explorer. Every single one of their mice died within 6 months after they had them. Pretty sad if you ask me, not to mention the ergonomic feel can't touch the Blue Optical Logitech mouse.
I'll agree that the Dual Optical mouse's shape is nowhere nearly as good as the blue optical, but I prefer it over MS's new Intellimouse shape, which strangely (lol) resembles the Logitech blue optical design.
I'm curious to see what Microsoft will release to conter this mouse, if they're going to even bother trying.
As for the Blue Optical, the day mine dies (knocks on wood) will be a very sad day, and I second whoever said that a good mouse is worth every penny. It really is, I paid $50 for my Blue Optical and I could not be anymore satisfied.