While pair programming I will say something like "just click on it with your mmb" and I always hear "what's that do?" I have yet to work with a single developer that uses the mmb. I live and die by mine. This doesn't include the "I don't have a MMB" Mac club.
It is quite handy as a clipboard in Linux distros.
That said, I learned the hard way the switches put for MMB are often subpar and fail quite fast. I replaced an Omron (?) switch in a Logitech mouse... twice. Thankfully the current Corsair M55 (pretty basic wired gamer mouse) goes strong.
