I've got a pile of old mice, both 1- (Apple, of course), 2- and
3-button, serial, RS232 ADB, USB and PS2. I can't recall ever needing
to use or using the middle button a 3-button mouse.
I did train myself early on to use the mouse left-handed or
right-handed. When working with graphics, a mouse is a killer for RSD
for me.
I've got trackballs (CH Products) as well as a couple of Cirque
Glidepoint pads and briefly toyed with getting a foot-operated mouse
wheel-thing.
None of the alternatives worked as well as a plain old mouse.
--Chuck