Three days of field tests that began with swiping a larger mouse off the desk of a coworker who has been out of the office lately seem to support my theory. When the pain eased after a single day of use, I quickly ordered a Logitech Professional MX. After three days, the pain in my wrist has practically vanished.
Something else that pains me is that I adore my Magic Mouse and Magic Trackpad. Alas, I am passing those on to others and digging the Pro MX.