Computer mice often have scroll wheels or multiple buttons. The middle-click function works as a shortcut in many programs; here are some tips for using it.

Macworld At a glance Expert's Rating Pros ・Sturdy, comfortable design ・Horizontal and vertical scrolling wheel ・Programmable ...

Huh, I middle-click the scroll wheel all the time. Couldn't live without it. The only one I recall struggling with was the Logitech M535, which took more strength to press.