I really don't see why anybody would "upgrade" to Windows 8. The GUI is of the type you see on tablets and phones ... but they'll be shipping it on desktops and laptops too. In addition to that, there really isn't anything about it which is an improvement over Windows 7. From what I've been reading, not too many business are going to be jumping on Windows 8 in a hurry, probably in part because doing software training is expensive and time consuming.
I'm not at all a fan of Apple, but their method of changing OS X incrementally over a long period of time seems much smarter than what Microsoft is doing. Windows has had the "Start" button since what, 1995? And now it's gone. People are going to freak out.