Unity and Gnome3 had maybe a year of shitstorms before it died down to some grumblings here and there. Metro has been around for two years, and one year for desktop Metro. It's getting on time to move it along.
It's only been around for nine months or so on a platform with an actually significant number of users: XBox 360.
It's coming soon to a platform with something like ten times the number of users the 360 has: Windows. So there's going to be a lot of people encountering it for the first time over the next few months.
It gets old. I'm getting tired of sounding like a Windows 8 fanboy (I'm actually fairly ambivalent) just in comparison with the ridiculous hyperbole and FUD being spewed here constantly.