(With how many creative people there are doing web work nowadays I'm always amazed that design trends seem to stem from the most recent/popular OS.)
What's great about the Metro style is it makes responsive layouts dead-simple and it cuts the design process down considerably. Sure it looks boring, but that's okay for now because I spent years hearing about wet floors and jelly buttons and skeuomorphism and...
It's refreshing to be able to pick a few colors, pick a few fonts, put it on a grid and be done. To me it almost feels like laziness, but it's a nice change of pace from the days when a single button took hours to design/build.