That may be true for some apps, but it doesn't always work as advertised. Mail, for instance, takes up the whole display even if I don't have any email showing. The maximize button on iTunes doesn't even maximize, they overloaded it to display the miniture controls (so I don't see anyway to do it unless I resize manually). In Quicken, the register doesn't work as you describe. I can go on and on. I need a way to explicitly say maximize vertically. While the smart maximize is a nice attempt, it doesn't always do what you want.
--jeff