After almost 20 years of running Linux, FreeBSD (and even NextStep!) on x86 bare metal, I've for the time being gone back to Windows.
It's a fast dual-head box. One screen is all Windows (and I'm typing this from IE 10), and the other is xmonad and emacs on Arch Linux on VirtualBox.
I'm also an Apple user (and AAPL shareholder), owning two (2010 and 2011 model) MBPs, and it is my opinion that Windows 8 is gorgeous and very, very stable. Microsoft has finally simplified the desktop experience, with sane security defaults, and in my opinion are very close if not at par with Mountain Lion on ease of use and attention to detail.
Finally, the system's performance as a desktop machine is at least %25 better than Unity/Gnome 3/KDE, and the overall fit and finish is years ahead of any leading open source DE. It was the Desktop Linux experience that has encouraged me to look elsewhere.
I'd encourage everyone to keep an open mind wrt MSFT. They're on the right track. This is not the same company I grew up hating.
Although I haven't tried Windows 8 yet, I had the same experience using Windows 7.
It's interesting that only 7 years ago you probably wouldn't have be able to sit me in front of a Windows machine without resistance or at least some complaining. Since then I turned out to be a frequent defender of Microsoft in my surroundings and I'm considering ditching my Apple ecosystem for Windows 8 (esp. because of Surface and Windows Phone 8).
But the real problem, as have stated other, is OEM software and 3rd-party-apps. It takes effort to maintain your system (although not much, at least in my opinion, but you have to pay attention to, for example, what is installed along the way). I usually have none of the problems my peers or friends have (with Windows) and if you look at their machine, you'll see why. Almost every time I visit my father, there is a new (worthless) toolbar installed.
Sorry, but the skeptical in me says this comment reeks of advertising. I don't know if it was your intention or not, but it feels like you try really hard to establish "geek cred" and then make some grandiose claims about Windows 8. It seems like you were comparing Windows 8 to a really non-standard Linux environment and then out of nowhere you claim performance is at least 25% better to three DE's which weren't in your dual-head box. Odd.
Extraordinary claims need extraordinary proof (some benchmarks, maybe), you are not providing any of that.
Your setup is close to mine, which is Win 7 running VirtualBox and Linux Mint. I've not used a Mac. I like developing with Linux. A friend recommends ditching my double-OS setup in favor of Apple. My question to you is, why don't you use only Apple / Mountain Lion? Why bother with Win 8?