I'm not a fan of Windows 8, but I guess the UI of Xbox One isn't that bad. I mean I don't have any issues using it since we have voice commands that are available. It would probably be an issue for me if the voice commands were disabled.
Yup, it's just based on Windows 8. It takes some elements like the UI and animation but it's Xbox One's UI. Xbox One's UI still misses some elements from Windows 8 so it has some uniqueness to it at least. There are some elements in the UI I actually like more than Windows 8.