To share our internal testing (small)...
We just completed testing W8 CP and we specifically looked at efficiency, work done versus time spent. After 3 solid months of testing with 27 client computers, this is what we found using desktop computers. The machines used hardware based on mid 2011 spec'd items.
> Factoring in having to get used to Windows 8, average weekly productivity was approximately 33% worse than with Windows 7.
> Without factoring in the learning curve and strictly looking at the highest levels of Win8 productivity during the testing period, it was found to be 18-20% less productive than when clients were using Win7.
The key complaints we found during our survey are the confusing locations to alter settings. Instead of having just one location in the Control Panel, they now had to look at more than one place . The lack of a Start/Win button was huge, nearly everyone was greatly affected the first day due to that change alone and severely impaired the user's ability to easily navigate around, trying to find out where to shutdown or restart the computer. We had people getting stuck prior to the login screen (lock screen), something we never ran into before with any previous versions of Windows.
Metro was a hit and miss, many found it cool looking but found it less than useful on a desktop computer.
Nearly all didn't like the overly plain look of many of the apps, they found the large, thin fonts very unappealing.
Our internal survey showed 26 of 27 users found nothing beneficial about Win8 where it was clearly better than using Win7.