The reasoning for the global menu bar isn't just about saving screen space. It's also about reduction of UI chrome to provide an interface that looks cleaner and simpler. Mouse travel distance *is* irrelevant since mouse acceleration allows for great travel distances from short, twitchy movements. It is also easy to hit the menu, as it's on a screen edge and easy to hit vertically. I work with a *trackpad* on a very large monitor, and of all if the pointing issues I have, the only serious one is when I need to aim in two dimensions.