The Rollermouse/Pro/Free is a top shelf design in most ways. I am confident if someone has RSI issues (I don't) that it is a possible solution.
It is not meant to be used with a tall or curved keyboard. In spite of this, I use it with my Contoured just because it works so darn well and is so pleasurable to use. Also, to me, using a mouse doesn't seem to make sense (hand away from keyboard, moving arm-wrist-mouse to move curser...). Stone age age stuff. I'm more of a a trackball, trackpad, trackpoint kind of guy. You can add Rollermouse and Mousetrapper to that list as well.
The only items that annoy with the Rollermouse me are:
-Sometimes when you move the roller horizontally and it stops before the curser reaches the target. That's a mechanical function of it's design. It has micro switches when you reach the end, but I use acceleration, so the curser flies out of control. Other solutions?
CORRECTION: Contour Designs has drivers that allow for horizontal scrolling.
My Rollermouse buttons are easy to press, and the scroll wheel is fine. Although Contour Designs is helpful, they cautioned me not to open the unit, but I found it easy to open, take apart, play with the parts, and put together. It's a very clean and simple piece of equipment, and my confidence increased after seeing the guts. You can pretty much almost make a Rollermouse Free from a Rollermouse/Pro unit. I may do that to mine. As far as going from a Rollermouse to a Rollermouse Pro, in my opinion, there doesn't seem to be much of a reason unless you are buying used at an under $100 price. Also my opinion, the Free is much more awesome if it had a $150 retail price. I would like to hear others opinions on Rollermouse verses Rollermouse Pro verses Rollermouse Free.
To clarify: My occasional non -intended "double-clicks", my unit is 10 years old, I've moved 7-8 times, and have no reason to believe that the Rollermouse wasn't used as a Frisbee by the movers on at least one occasion. I think very highly of these units.