I wasn't quite sure whether to vote for "Sometimes" or "Always," as I frequently use the right mouse button but the left mouse button is more in use, obviously. I opted for "Always," in the end, because I virtually never Control-click anymore, I virtually always use the right click option where it exists. At the moment, I use a Logitech MX510 and use the right mouse button when clicking on files (eg. for "Get Info" etc.), when using a web browser, and frequently when playing games.