I'm naturally right-handed, but learnt to use a mouse/trackball with my left hand ages ago when I figured out the twisting/ergonomic issues with a right-handed mouse and a keyboard with a numeric keypad. I was previously prone to hurting my right-shoulder blade (pulled muscle?) as there's a constant twist compared to the mid-line of the keyboard.
I'm naturally right-handed, but learnt to use a mouse/trackball with my left hand ages ago when I figured out the twisting/ergonomic issues with a right-handed mouse and a keyboard with a numeric keypad. I was previously prone to hurting my right-shoulder blade (pulled muscle?) as there's a constant twist compared to the mid-line of the keyboard.