is it really necessary? I use CAD and Solidworks fine with my mouse lol.
Depends on the application. The support in animiation software was always lame so it doesn't help much there, if at all. Got my first space mouse with Superscape VRT (now defunct virtual reality software) and it was really well implemented. Left hand on the space mouse, right hand on the mouse for basic construction. With current animation software you have the left hand on the keyboard for shortcuts and the right hand on the mouse which makes it easier to do your viewport manipulations just with the mouse while the 3D controller would require to reposition the left hand.
Fun for fly-throughs though.
I suspect a dishwasher cleaning of the keys though. Watch it with the heat on the larger keys especially.
Never had a problem with IBM keys.