I haven't used Win 8 in any way, not even a Windows Phone device, though I am slated for "training" tomorrow morning. So, just getting that out of the way, because there may be some specifics I'm not aware of... Yet.
Being kind of an enthusiast psychologist/sociologist, I see something of a pattern with Windows releases. Essentially the bigger the changes from the previous version, the more the initial resistance to the release. You can go all the way back to Windows 95, 17 years ago, which adopted the look and feel that was to be used for the next 17 years through Windows 8's "classic" mode. There was a fair amount of resistance to Windows95 because it was a pretty radical departure from the old Windows 1.x-3.x Program Manager interface. Fast forward to XP, and everyone was moved from the old DOS based version of Windows to the much more robust and modern NT platform... Suddenly everyone had to come to grips with user accounts, permissions, driver support was rather poor, the OS actually enforced rules about directly accessing hardware by programs and so quite a few programs wouldn't work (mostly games), integrated chipsets at the time couldn't handle the Luna skinning system very well. Now fast forward again to Windows 8, and you have another rather radical departure from established convention, with the predictable resistance to it.
Along the way, you can point out how when you boil it down, most of the complaints people had about WinME were "they moved things around." That is the majority of what Vista complaints boil down as well, along with another case where low end hardware being branded as "Vista compatible" was kind of misleading because it really wasn't up to the demands of Vista.
There are a few moves on Microsoft's part I question, like making the Modern UI the default even for desktops. Tablets and cell phones I could see, even making it an option on desktops, but just not making it an option to set the old Windows Explorer desktop as the default. However, at the same time, how much does the average person really use the Windows Explorer desktop as much more than a glorified program launcher? If you can do that with Modern UI, and switch between programs with the same relative ease, then what exactly have you lost aside from the security blanket of the familiar?
Personally, having always been a fan of the old Program Manager style interface compared to the Mac OS style desktop, I'm cautiously optimistic about Modern UI. I think it will need a little refinement for the desktop, but it has potential. At the same time however, I could go off on a large rant about how it seems like Microsoft and Apple are both turning desktops into vastly overpowered tablets rather than seeking to differentiate the two and exploiting the unique strengths of each platform, and the ways in which they might compliment one another. Might still be a little too early to comment on Microsoft, but Apple seems firmly set on the path of iOS being the only platform going forward, like it or not.