I think the problem with Windows 8 is anything Metro. WIndows 8 is actually pretty good. It starts up faster than 7, has some small fry interface improvements (like the file copy dialog, some more task manager data), etc. But it defaults to wanting to start everything metro, and metro is really made for single touch screen laptops/tablets. Which on a desktop, is just irritating. Once you get rid of all the default associations, you don't need to install classic start or whatever, it's mostly unnecessary once you get used to just opening up the metro start menu and typing what you want, it's usually pretty decent at finding it, and even in 7 I mostly just pin the things I want to the taskbar.
Also, it has some good shortcuts once you learn them. win+x, win+i, etc.
Though being able to run metro apps in a window sounds interesting, though I think MS is going to do that as a standard feature. I'd probably be more interested if there was a single metro app that I'd actually want to use.