I developed pretty nasty tenosynovitis in my inner wrist from using a Magic Pad over a year. I even tried switching to using it with my left hand instead of my right, and eventually developed the same problem in the other wrist.
It got bad enough I opted for cortisone injections.
This was about 10 years ago. I’ve avoided Apple’s input devices since, opting for proper ergonomic keyboards and mice, with no further RSI thankfully.