Kensington Turbo Mouse! Worked like a charm for me from the first time I used an auction $5 unit I purchased and have owned a dozen or so over the years. Good solid products with solid easy to obtain software. The bigger the heavier ball the better! Also you can substitute the balls on the old models 2.25" billiards work nicely.

Wrist support is Mandatory for prolonged use otherwise you will have a problem with cramps ... but that goes for all inputs.

I use the Expert with scroll wheel now that zooms and pans in my cad software - very usefull - but the scroll could be more sensitive.

However I like to have seperate input devices for every computer in the house to help my slow head twig to the machine characteristics.