I use an Evoluent vertical mouse. It is a high dpi mouse, but the position is not as precise as a regular mouse overall since you basically move it from the elbow instead of the wrist. It has two features that I love:
1. It has 3 distinct large buttons AND a wheel, so I have the best of both worlds with a real Middle Button. This requires running a separate button remapper on x64 which is a free download
2. I can use it for hours with no wrist strain or irritation
With enough practice the precision is not a problem.
http://www.evoluent.com/
Evoluent here as well.
Best mouse I've ever had.
Standard Dell 7 button.
My Evoluent is gathering dust. For me, it's extra buttons aren't easily accessible. With my dell I have easy access to 3 extra buttons (left wheel tilt, right wheel tilt, thumb in addition to left/right/middle). Also, I found the wrist position to be stress-building over time (then again I only used it for a week - maybe this goes away with extended use???).