The right thing MS should have done is to leave the tried and true UI design in place when working in a windowed environment, and when the app runs in fullscreen like on a phone or tablet, then have minimal chrome. We already have the ability to let the OS render the chrome, so the app is already portable between different environments. How does such a design exclude a write-once-run-anywhere goal?
They could keep the ability to clearly see focus without having any extraneous chrome. Adding color to the focused window title bar, but getting rid of all the "pretty" glassy effects, would solve a lot.