This is an animation. Made such way like a title animation on television shows. So this has nothing to do with an actual OS. It isn't a screen capture video, it isn't a skin or theme.
These are my ideas that I would put into the new Start Screen of Windows 8.
- Customizable background image
- Layered background and sqaures movement when scrolling through items,
- Livetiles with AERO GLASS,
- Livetiles with changable corner cuts,
- Livetiles with video support,
- Livetile group labels with brand & product logo support (.png),
- Hardware detection notification feedback redesign,
- Rotating circle as hourglass,
- Windows Phone 7/8 integration, e.g.: you should be able to write and send SMS through Windows 8 with USB/Bluetooth/WiFi connected WP7/8,
- Animated CHARMS and right side panels with AERO GLASS,