At the risk of turning this into a medical thread ...
Please confirm that if you have wrist problems caused by years of abusing mice resulting in stiff painful wrists, then these things can help if used carefully and sensibly?
Yep.
A relative of mine had his arm crushed under a hydraulic press at work and it pretty much rendered his arm dead. After about a year of therapy on it and such the physio finally gave him one to use lightly a few times a week. It worked wonders and helped to rebuild the muscle in the arm that had been lost through many months of no use in the arm.