I started by upgrading my laptop to 8 to test how it is (I don't use it that much anyway). I believe I can get used to the tile screen in itself, that seems like a nice and powerful tool. I also like increased performance (start time especially), the new tools are great (task manager) and Skydrive's integration is working quite well (though slightly slow to upload/download documents, but that might be my laptop's fault). Overall, I'd say the underlying O/S is a nice increment to W7.
What bothers me the most about 8 so far is the doubling of applications and/or configuration. It just does not seem to serve any purpose on a desktop. Granted, I can pretty much remove all of the applications I do not want, or simply assign file types and actions to whichever application I prefer, but the configuration by default should still be better than it is at the moment.
I'm a bit scared to install W8 on my main computer; I have a dual monitor setup and I've heard some people complaining about their setup not working very well in 8.
What scares me the for Windows 8 though is that people, especially enterprises, will not switch to it. There's just no way. I work daily with all sorts of people, most of whom are very well educated, and they will have issues working with Window XP/7's UI. That's an interface which has been mostly the same since 1995. I just don't see how a company would scrap all that and switch to something that is less intuitive.