> You all know the Dock, it’s been at the bottom of your Mac screen for what feels like forever (if you keep it in the correct location, anyway).

On a website with huge margins at the sides. I think the OSX Dock is a pretty good thing, but it makes so much more sense to keep it on the side of the screen and preserve vertical pixels. Unlike (some versions of) the Windows Taskbar, the icons are all square with no text, so you're not even sacrificing readability.