I just upgraded to the latest Kensington mouse driver
(they use one for all their products, but for reference
my model is called "MouseWorks" and is USB and pretty
modern). This is version 1.1.
They just added support for "Middle Click", primarily
for Maya under OS X I believe.
So I tested with xev, which is great for debugging mice,
Physical Button xev result
Click (1) Button 1
Middle Click (2) (nothing printed at all)
Right Click (3) Button 3
Scroll wheel up Button 4
Scroll wheel down Button 5
As you can see, its almost perfect :) Lots better than I
ever managed under Linux.
But I'd like it if I could have a "true" middle button
(ie, generate Button 2) so I can turn off emulation
Please contact me if you need help with anything and
don't have any Kensington hardware to hand...
(I know I can use emulation to work around, thanks...)