It's Windows 8 on a USB stick—full operating systems and user files—that you boot to on another Windows PC. It won't have access to the PC’s hard drives; just the USB data space.When finished, shutdown, remove stick and the computer reboots to it's original O/S configuration.
Caveats: It has to be a USB 3.0 with at least 32GB free space. I've made them on as small as a 16GB 2.0 stick, but awfully slow to load. 3.0 is definitely fast to load and run!
This let's me carry my desktop around with me. As long as someone has a system that's bootable from USB and a USB 3.0 port, and they'll let me use it ;->
Win 2 Go is interesting. But, for me, the possibility of being able to boot an image of a work pc on a different device loses much of its value when the image is removed from the context network / workgroup and the resources available therein.
Secure Boot is impressive, and is the most compelling reason for me to consider an upgrade.
The Metro UI makes sense on a phone or tablet, or maybe even a touch-screen enabled PC. But for the existing base of installed screens... I’ll be using the Win 7 UI mode.