It's ok, I really don't know what kind of score I would give it. I really don't delve much into it, I just use the desktop and the file explorer, So other than shutting it down or starting certain programs I make it act almost just like windows 7. You don't have to use the metro start screen crap, I don't.
People keep saying it is horrible, but I don't think it's that bad at all. The metro interface I don't use that much. I have touch screen, but I don't use it very much. To me it just seams like an improved windows 7 for the most part.
For me, the Windows desktop side seems pretty good I would give that something like 7 or 8 out of ten. For the Windows App side (Modern UI, Microsoft don't want you to call it Metro) looks quite good for what it is, I would maybe give it 6 or 7 out of ten.
Put them together for a desktop OS, I would say 3 to 4 out of ten. Windows 8.1 is a bit better but still falls short.
I like the simpler flat theme. Don't care much for the metro side but then I rarely have a need to use it. I read about certain optimizations to the internals that make CPU and memory use more efficient, which is cool. Other than all of that it's practically the same as windows 7 for me.
8/10 I guess. I don't think it's as "different" as people believe. The way I see it it is the same old windows with some modern additions.