I've never had any computer-related pain (well, not since the lengthy gaming sessions of my youth), and my current typing ability is more than sufficient, so I guess my impetus to switch is tiny.
The problem with tendinitis, carpal tunnel, bulged neck discs, and health issues that afflict programmers is that you don't know you're susceptible until you already have the problem. Then you're looking at months or years to fix it and learn techniques and equipment to avoid its return.