TLDR: Windows 8 isn't perfect, but it's a stepping stone towards what I want from a modern computing environment.
I was a fan of the "Metro" interface, first on Windows Phone and then on Windows 8. However, I've been studying my use of my PC and find that I rarely use the Start Screen.
Most of the time, I've got Visual Studio full-screen and all my work is done in there. I tend to use my phone and tablet (Nexus 7 until we get a Surface Mini) for most of the other stuff I would have done in the past on a PC (Browsing, Email, Skyping, Messaging etc.)
So whilst I like the concept of Live Tiles, I rarely see them on my desktop PC. What would be more useful is a notification centre, that I could view at the click of a button, or even by hovering at the edge of the screen like the charm bars.
I'm still a big fan of WINRT, we've needed for a long while to get away from Win32 and I think that is where Microsoft needs to spend its time, both in a "Window" and the full-screen experience. A modern API for modern application scenarios. Cross-platform across all devices (including Android and iOS)
I am a fan of the "Modern UI" design guidelines and also liking the "Material" design that Google announced recently. Also liking the "continuous client" approach that Apple seem to be taking.
We are in a period of slow evolution, as we moved into a multi-device world. There will be a few wrong turns, but there always have been in the history of computing.
I know that what I have in Windows 7 doesn't give me what I need for how I work today, Windows 8.x is getting closer by giving me WinRT and apps that work across platforms, but that is more down to the cloud and WinRT APIs rather than the Windows 8.x UI.