Interesting to see the first official video of the new Windows Phone based interface that's coming to the desktop next year. Of course this is just an early pre-beta, but by all accounts Microsoft are serious about moving towards a simplified touch based interface that'll be similar across desktop and mobile devices.
A bit strange to see the Windows GUI moving away from actually using windows, in favour of a tiling window manager where everything opens maximised to full screen. I can see how that could be less confusing for new users, and work well on a touch screen, but it seems highly restrictive to me.
The last version of Windows where applications had to be tiled, without stacking and overlapping of windows, was Windows 1 back in 1985.
From:

To:

Very shiny and modern looking, but in some ways Windows 1's window management was actually more versatile, as you weren't restricted to splitting the display between two applications only.
The traditional Windows desktop still exists in 8, but only to provide compatibility with pre-Windows 8 applications. You can't switch off the fancy new UI, bring back the good old taskbar and start menu, and run those new apps in overlapping windows over an icon strewn desktop.
It's probably the biggest change Microsoft have made to the Windows UI. So big that it's bound to be highly controversial, and I'm wondering if they'll back down and make the new UI more optional than it currently appears to be.