It's going to take some getting used to. It doesn't compare in looks to the Pro Mouse. Strange that they couldn't make it look better. But it's about time Apple released a new model to satisfy the need for a more powerful device. Features include left and right click, a 360 degree scroll button, and two side buttons that actually work, not like its predecessor's. The price tag is $49, compared to the opening price of the Pro Mouse (it's now just called "Mouse") several years ago at $59, now reduced to $29.
I'll wait for the hardware reviews to see what they say. If they come out with a wireless model, I'm sure Bill will get it. But as for me, I'm keping my one button device with me.
EDIT: Now they say that it's officially compatible with Windows XP, though Apple mice almost always have been.