I'm switching because I get sore wrists, forearms and shoulders from so much computer work. Often I have to switch which hand I use for track pads and mouse moving.
This happens especially when using a track pad on a laptop with my right hand. My right wrist hurts in a repetitive stress injury way and my bad shoulder hurts from inactivity and lack of range of motion.
I've been using a pair I think I got from Ace Hardware, or maybe Agway, but they are basically like these.