Apple didn't lift anything from Xerox, they got the rights from from Xerox. Not revolutionary, it they only invented the Menu Bar, Modal Dialog Boxes, Overlapping windows that don't flicker, and of course Drag n Drop i.e. click, drag, release with only a single button. All of which revolutionized the GUI experience we still use today. The PC revolution started with the Apple ][ and VisiCalc (the first killer application) that brought the PC into business.