Valuable work space? Seriously? The Menu Bar is less than 3% of the height of the screen. What can you possibly do with 100% that you can't do with 97%? You can't hide title bars in Windows, so why would you expect to do that in OS X?
I like 16:10 aspect ratio vs 16:9 which is found in like every notebook now. That menu bar eats away at the available vertical space.
Try reading same PDF file (side by side view) at 1920x1200 using bootcamp then with OS X. That top bar gets in the way
Even Windows displays the menus all the time.
Not true you can hide the start menu and it goes away