I think there's some really great parts of the Modern (aka Metro) UI, but there's other things about it I hate. I love the live tiles homescreen. It's unique and fun and actually really useful. The canvas menus, with the left-to-right navigation? Those are neat, but the Modern UI makes titles (like in the People Hub) ginormous and the title alone takes up a third of the screen. Then the rest of the way everything is laid out looks messy. I think it's because the fonts are too big in general. That put me off big time. Screen real estate is wasted.

The general look of the flat icons I like. And you have to give Microsoft some credit, in 2011 Android was on Gingerbread and Apple iOS 4/5, neither which had flat elements as a pillar throughout. A few years later and things have changed in a big way, most notable for Apple and iOS 7.