Metro was terrific on mobile - especially for older people who had no issues reading information from tiles or navigating sharp interface. Once my mother's HTC 8S broke and she had to temporarily switch to iPhone she complained how the interface was small and barely readable. It's the desktop where it failed - you can't just force users into a mobile interface, at the same time remove the most recognisable element of your product (start button and menu) and believe people will adapt.

What I find wild is that there were internal W8 releases with a proper start menu but they abandon it at some point to fully embrace Metro.