There's a lot more potential for repetitive stress injury (e.g. carpal tunnel) with using mouse on one hand constantly. At least with a keyboard, you are distr

There's a lot more potential for repetitive stress injury (e.g. carpal tunnel) with using mouse on one hand constantly. At least with a keyboard, you are distributing the stress among four fingers and a thumb. Although, admittedly I use my right thumb for space rather than alternating with my left thumb.