Microsoft did not build a bad OS by any means. As someone who can take this learning curve, I really enjoy using it on a tablet (I think it's much superior than iOS and superior to Android when it comes to the core OS), and I also like its Metro features a lot on my desktop. What Microsoft did very wrong however is building this interface for an audience where the overwhelming majority is not willing to take this learning curve. It's simply not built for the "average user".