If you're looking for the absolutely best mouse on the market, it's the Logitech
MX700. OCIA plays with one, check out what they thougth here.
The MX 700 is the most comfortable mouse Ive ever held.
It fits perfectly to my hand and none of the buttons are uncomfortable to use.
It features eight buttons in all: the normal two buttons, a clickable wheel,
a button above and below the wheel for scrolling, another button below the wheel
for task switching, and two thumb buttons for forward and back commands.