UI wise it's just a mess. It's 2 different ui's badly bolted together, the primary one of which is designed for a tablet, not a keyboard/mouse that it's actually being used with.
They basically developed it for the surface pro - so they sacrificed the 500 million or whatever keyboard/mouse users experience for the 5 or less million surface pro users. It doesn't even work well for a tablet because half the programmes need the desktop interface which is rubbish for a touch screen.
In that way it's the worst windows ui MS have ever managed to produce - in the past while flawed at least it was schizophrenic.