Me too. Due to some issues with right hand I retrained myself to use mouse with my left hand. Now I can use mouse by both hands, and in both button orientations.
Switching is easier than most people imagine, IMHO. I started to feel the beginnings of an RSI and went from right to left for half a year or so, no problems.
You basically just convinced me that I should be training my left hand to use my mouse. In all cases except precision work (eg graphic design) it should be doable.
Side note, but if you actually do graphic design, get a digitizer/gtaphic pen tablet, it is simply "another world" when compared to mouse, nowadays even an el-cheapo one ( i.e. something in the 40-60 US$ range)is good enough for non-professional use.
