I'm right-handed and use the mouse predominantly with the right hand, but occasionally with the left. I feel like my deficit in mouse ability with my LH is much lower than, say, my deficit with writing LH. I can do it nearly as well LH without a lot of extra practice as I can RH.
I don't know if that's typical of other people's experience, also?
I could understand then using RH, just because the keyboard/mouse relationship was not really well-designed for sinistrality.
That kind of reminds me of my pet project... I am making an effort to play all my stylus-based DS games left-handed (stylus in left and right hand on buttons). It's been challenging, but I've been progressing through Trauma Center, Metroid, and most recently Brain Age in this way. 🙂