Personally
Just received my "official" Windows 8 physical CD from MS that I ordered as part of their £14.99 upgrade plan for Windows 7 computers. Needless to say, in the month it took to arrive (luckily they *do* give ISO downloads, but a lot of people on that offer must have had to wait a month to get an install disk that they didn't know how to use, methinks) Windows 8 Pro itself hasn't managed to work its way out of a VM and onto my actual computer.
In fact, in anything, it's probably sleeping quietly inside the confines of its quarantine, waiting for the day that it sees light. Bear in mind that on the machine I installed the VM, it's a brand-new Windows 7 machine and the first I've personally had running that OS (I've trialled it and tested it and done lots of work with it, but never on my own personal machine which has been XP for YEARS). It would have been a cinch to ditch the fresh Windows 7 Home Premium install and then put Windows 8 on and skip Windows 7 entirely.
The Windows XP -> Windows 7 migration? Pretty smooth, given that it's still on there and I haven't needed to exorcise it yet and the computer gets 16 hours of use a day for everything from work to games. Sure, I needed to polish it up a bit and plug some holes with freeware and its far from perfect but it's certainly usable without major hindrances.
But Windows 8? I spent a day getting a "Active Directory Users & Computers" icon on my menu - so much bad software installation and dead-end error codes that it was unbelievable. Got there in the end (apparently it's my fault for installing from a VM network share, using en_GB as the system language, and wanting to disable automatic updates and Windows Search, which are obviously the FIRST things you look at when the install program for RSAT just crashes with random hex codes that mention none of the above).
I could never get the file management windows to be vaguely productive for me and I'd get more done using a third-party shell than I would windows explorer now.
If it wasn't for the fact that it was only £14.99 and that gives me "8 Pro" which I can use to manage networks if it comes to it, and I can keep it snoozing inside a VM until I actually *need* it (which is likely to be very infrequently), I wouldn't have touched it. The same tricks applied to 7 don't apply to 8 and there's some things that you simply cannot do and I couldn't get it to the point where I could actual feel productive using it. Even the "Server Manager" junk I'm dreading having to use, and when I do, I'm likely to use VMWare's "Unity" feature so that I get the Windows 8 Pro windows from the VM overlaid into my Windows 7 desktop as if they are native apps.
Seriously - I have a "free" upgrade any time I like, I'm fresh off of XP and thus mentally prepared to put in the legwork to get to a productive desktop, I have the software installed, properly licensed, an "edition" upgrade to give me more features, even a free Media Centre key for it (not that I'll use that feature for anything except the DVD codecs), entirely compatible hardware, and still I can't justify actually *USING* Windows 8 over Windows 7 (or even over XP).
And still I haven't figured out how to lose the Language menu on the taskbar (which is required because I *have* to have the en_US language pack for the RSAT tools to work), or the "Touch Keyboard", both of which come back after a reboot no matter what options or registry entries you tweak. It's just like a bad, untested Windows 7 service pack that no-one wants to touch - it's exactly like installing Gnome 3 on top of your perfectly-working system - the underneath is the same but the interface is just too horrendous to use even if it comes "for free".
Windows 7 gets used 16 hours a day by someone who stuck with XP up until this October (quite glad I left it that late, because without the existence of all the freeware and tweaks I want to do to it, I wouldn't have touched it).
Windows 8 gets used once a month to do a Windows update on it, from inside the Windows 7 VM host.
You could offer a free Heidi Klum blue movie with every copy, and still you'd have problems shifting it.