The preview showed today is the OS for: PCs, hybrids like the Surface Pro and the Asus T100, and big tablets that offer compatibility with x86 apps like the Toshiba encore 2 (10-inch) and the Hp Omni 10.
Sadly, this version is mostly a desktop OS optimized for mouse and keyboard. The touch UI is an horrible mess, an afterthought.
I understand they want to secure the PC market, but to make happy the Windows 7 users they dismantled the touch aspect of the OS. Maybe a bit of geniality could had prevented the fatidic outcome, but no, they couldn't solved it, this is just Windows 7 with live tiles, and a ridiculous "continuum" UI unfit for touch devices.
Of course tech bloggers are praising Windows 10 because they only see it as a desktop OS, but with the focus in the touch interface I only see mediocrity and failure.
They'll show the ARM version in early 2015, here a glimpse:
http://wmpoweruser.com/first-tablet-running-windows-phone-pictured/
Just a scaled up WP.
The major design decisions can be changed in so little time, It took a couple of years to develop what they showed today.