The thing I personally don't understand is why didn't Microsoft just do the same thing that Apple does with iOS or whatever? Extending the Windows Phone platform from mobile phones to tablet "PCs" and keeping the traditional desktop experience for traditional computers, both desktops and laptops, doesn't sound bad at all; there would certainly be more hype in the tablet market.
As it is now, I feel like Windows 8 gets to be a bit risky to use in terms of security, with all those different possibilities the Metro UI brings. It's distracting from things that need to be done, which is rarely a good thing for power users; not to mention that the Metro UI and the traditional Aero UI don't match - not even close. They should've chosen one and stuck with it. Though they claimed otherwise, it LOOKS just like they simply built Metro on top of the Desktop, despite their statement that this isn't the case.
To me the whole MetroUI thing just looks like a colossal commercial for Windows Phone OS - users that like its possibilities would probably (and that's just my assumption) consider getting a WP rather than an Android or something.
On the other hand, I can understand that, with MS' 3-year cycle of new OSs, Windows 8 wouldn't bring much improvement over 7 without Metro, or I guess that's at least what MS thought; but the thing is: IT DOES! I wouldn't mind "having" to upgrade to Win8 for performance enhancements and tweaks and things that updates for Windows 7 can't achieve. This is also why I preferred Vista over XP back when it was released. XP was a system quickly left to rot from the inside while Vista had shiny (and I don't mean that literally) new looks, updated system apps...
The progress could be felt! Windows 8 doesn't really have that as a whole package without Metro, but if they had split those two ideas from the very beginning, we would have an extended WPOS for tablets and something truly awesome for desktops and laptops.
Chicken doesn't go with cake, so why should I use Metro on top of my Desktop?