Windows 8 is OK. What I find problematic about it is that the traditional desktop and Metro seem to clash with one another even though you can use them both simultaneously. On the outside you want to pick which environment you want to spend the most time in; if you want to stay in Metro, then use only Metro apps, but if you want to live in the Desktop, then you find yourself avoiding any Metro apps. It's just too hard to mix the two together.
Assuming, however, that you just want to use the Desktop all the time, Windows 8 is not that big of a deal. It boils down to the fact that they took away the start menu, and that apparently drives people nuts. Personally, I don't even like the start menu. The programs you use all the time end up being pinned to the task bar, and for the occasional other program, you just hit the Windows key and type in its name. It's really not hard, but people just don't figure this out. My uncle got a new Windows 8 laptop last week, and right when he got it I told him three or four times to use the Windows key and type in order to search for the program he wanted, and he *still* would just open the start screen with the mouse and then open "All Programs" and sit there reading all the entries in order to find the program he was looking for. A few days later he said, "You know, I realized I can just hit the Windows key to switch between the Desktop and the start screen."
I would consider Windows 8 to be an upgrade from 7, but people struggle with the interface changes. Windows 7 has a more "pure" UI experience, and it's what people expect.