Windows 8 may work in an office environment if the users are solely in fairly simple one task Metro applications, with a more logical method of shutting down / task switching. I am fairly sure if users had 3 or 4 basic programs, which didn't need to interact with each other much, with appropriate lockdown and controls it may work alright.
Once you start messing around with desktop applications, and opening files in explorer which launch Metro applications to view / access them, then the trouble starts. Equally once you start doing any real complex work, for example you may be word processing, and need to refer to something in another window, then a loss of context from switching from full screen program to full screen program is for many users disruptive to their workflow.
I have had to support users who have Windows 8 installed. None of who were "power users" by any stretch of the imagination. Classic Shell and restoring all the file associations to work with desktop applications more or less made them happy, but the loss of context and continual jump between Metro and the desktop for them when trying to do basic tasks such as view an image or video infuriated them. They were much happier with the traditional Windows layout.
I spent about an hour getting used to Windows 8, purely because I knew a time would come when the inevitable "I need help with Windows" calls would come through, and although I got used to working with it, I found Metro particularly annoying and disruptive on the desktop, if Windows 8 was used as it was supposed to be used. In contrast getting used to the iPad and iPhone took next to no time. Of the other newer UIs I've recently delved into, Ubuntu's Unity at least followed a certain paradigm, and appeared to be the direction Windows 8 was aiming to go in if they had got it half right instead of totally wrong, and Mint's Cinnamon is an amazing piece of work, which any Windows XP / 7 user would feel at home in especially for something free developed by a relatively small team.
Windows 8 is for 90% of people an irritating waste of time, which has tarnished the Microsoft name further. Which is a real pity, as they got it spot on with Windows 7, perhaps their first OS since the days of Windows 95 which actually excited consumers, rather than was something they just tolerated.