The vertical mice moves the force of your actions from the wrist to the arm. Its perfect if you have wrist problems, though its slightly harder to do the really precise stuff like CAD. If you have carpal tunnel with your thumb or fingers, I don't think the vertical mice will help specifically with that, you'll just need to find the mouse where your hand rests the most comfortably.

I have used a vertical mouse but never long enough to get used to it. My favorite mouse of all time was the Steelseries WoW Cataclysm mouse Ugh mentioned in his OP.