I get various effects basically everywhere, but the biggest issue with M4/5, which I think would be similar with a gamepad is that the effort it takes to suppress the tremor feeds back and makes the tremor worse. I don't use my thumbs for game input much at all, now that I think about it.
oh, should have been more clear. I meant mouse buttons. 3 is middle click and 4 and 5 are the side buttons. M1/2/3 use a much different set of muscles than M4/5
