I usually just lurk here, but I didn't want anybody else to go through
3 different mice like I did (HP 3 button mouse, contour mouse,
evoluent mouse) before settling on the lenovo scrollpoint mouse. IMHO
it's the best option that's abundantly available, reasonably priced,
and comfortable to use. It has a real middle button and a scroll
"stick" instead of a wheel. You can rest the tip of your middle finger
over the third button and manipulate the stick with your finger joint,
allowing you to middle click and scroll without repositioning your
finger. Its biggest drawback is the lack of driver support for the
scroll stick on any OS except Windows. In linux and freebsd, the
scroll stick is sensitive to the point of being unusable. I don't know
how it behaves in native plan 9. The only reason I'm happy with it is
because I run plan9port in a linux VM with a Windows host, so the
scroll events are processed by the host.

Joseph