I've had some people think the scroll ball was the button, and were confused when their click triggered Dashboard.
I have the scroll ball button as my right click, its a super rapid setup as the mighty mouse has days when its a bit tempramental, so it avoids that, then just setup a hotcorner for dashboard, sorted!!!
One thing I hate is when people go "I'd never know how to use Macs. They're too complicated".
Right with you there, that is a major annoyance when people say that to me. Although sometimes I think its just the fact that they are covering up that they would want to try one but just dont want to change or take "the risk with it" as is unfortunately once of the things percieved about them.