Mac OS X, since the early version has excellent support for keyboard shortcuts. (Albeit tricky to configure.) And applications are always installed in one single location on Mac OS X - unlike Windows where some are in Program Files, some in Program Files x64, some in Windows, some in system32, etc. And applications on Mac OS are represented with a single user-friendly icon - not a folder with pile of subfolders where you still have to hunt for the proper executable. Bonus: the Dock (now also in Windows since 7) was always there to quickly access often used applications.
The Windows 8 start menu is populated with all newly installed programs and apps, hiding the extraneous bullshit under deeper layers that must be accessed specifically (as opposed to crowding your screen/menu with garbage like help files and uninstallers). Furthermore, it eliminates the need to care about where it is installed (unless you want to configure that, in which case that functionality still exists in normal programs, but not in store apps [at least not that I'm aware of]).
Hence why I love it (especially after using OS X for some time) and find 7 inefficient by comparison.