Just to chime in on this,
I have never used a mouse.
I have used a Kensington Trackball since
they were introduced in 1993.
But as was stated, things got a lil problematic
I now use an Apple TrackPad and would never go back.
Of course It has limitations.
1-not precise enough (in some situations).
2-not programmable enough.
but it is still by far the best solution for me.
The TrackPad to me is like learning to play a new instrument.
The gestures can be confusing at first but
once you get over the ‘brain bump’ this thing can fly.
So now I wait for Kensington to put the trackpad
and trackball into one unit.
I can imagine the surface of my trackpad ‘wrapped’ into a
360 degree ball and place in a trackball holder.
Now that would be kool.