Logitech VX Revolution. It is the little brother of MX Revolution, but is much more comfortable. Unless you have big hands, of course!
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Microsoft mouses are not good for CAD work! They have a hard to press and easy scroll middle button, while you need exactly the opposite to pan. I had one and returned it in two days!
I recommend also to use a high performance mouse pad. I started using a mouse pad because of my new glass desktop and was amazed by the difference it made. You never know how much a good mousepad accelerates your work until you try it! Best mousepads are the gaming ones. They are more expensive than ordinary mouses though!