I tend to use the mouse with whichever hand is convenient, although the buttons are generally a problem.

Maybe, Jon, you used the mouse with your right hand because it was the wrong shape for your left hand, and you then realised you had a world beating advantage over mere righties?! ;-)

I am left-dominant, but was brought up 'right-handed' - children in the Fifties tended to have to conform...

My feelings regarding instrument choice in general is that you will learn to play the instrument in your heart DESPITE the obstacles the world puts in your way.

As long as YOU are happy, sod the world!