I find that the design and structure of Windows Phone's UI is vastly different to the Windows 8 set-up. At least from my perspective. They look like cousins, but they function of different planes. It doesn't feel cohesive, and I think they did a much better job with their phones. The fluidity of Metro, the beautiful animations, the color palette, the system's language, and the way everything is where it supposed to be. Given the major backlash Microsoft got when Windows 8 was first released, I don't think I was the only person to have that opinion. I'm really hoping they don't start to mimic the way the Surface works.
I've been a tech-nut my whole life, work in Linux, have computers running OSX, previously had Android, used to experiment with Rockbox MP3 player firmware and all that greatness. I'm certainly not tech-illiterate. I just don't find Windows 8 all that intuitive or fun to use. It was that beautiful Metro charm that brought me over to Windows Phone in the first place, as well as its snappy response time and ease of use. All of those things represent WP; and they represent the opposite Windows 8 OS.