My issue with Windows 8 was simply that it was attempt to be all things to all kinds of users, with Microsoft insisting that you drink the Kool-Aid. Folks can pontificate about how the "desktop is dead" and that consumer devices like phones and tablets are the future ... except it ignores that large segment of users that actually use their computers for work.
If you're a large company, what is the real, tangible, bottom-benefit to retraining your thousands of cube-dwellers to use the new Windows 8 UI? When their tasks primarily are going to involve using Microsoft Office and [insert LOB application here], there is none. It becomes change for the sake of change that does not translate to any long-term productivity improvements, and actually incurs a short-term productivity loss. Simply put, the desktop metaphor may be "dated", but it works and it's what office workers have been trained to use for decades now.