I agree with Jonathan Marston, by the way great solution for the Charms Bar replacement.
This is my clarification about why Mac OS X have menu on the top of the screen.
X - Menus were introduced quite a while before the graphical interfaces. Was usually at the top. At that time only one application could be executed at a time. Some applications were able to open multiple documents using windows for that.
A - Apple followed to the letter the original idea presented in the “X”.
B - Apple updated the system so that it can run multiple applications on the same screen. The solution is to overlap the top menu according to the application in focus. Unfortunately this turns the menu to something confuse.
C - An acceptable solution to this problem comes only with the “Mission Control”, Applications and their windows now can exist alone in their own desktop bringing multitask in a clear way to Apple systems.
1 - Microsoft carries the application to a window, bringing the idea of multiple virtual monitors. Hence the “Windows” name.
2 - Applications with more than one window has to use the concept of MDI (Multiple document interface), windows applications are contained within a main window. Unfortunately this turns the window to something confuse.
3 - The solution was the extinction of the MDI. Each window of the same application behaves as a standalone application, some aplications share a hidden process, others run a new process copy for each window, this approach consumes a lot more system resources.