Microsoft has uploaded a video on YouTube that explains how they built the UI for windows
Here is another video showing the OS in action
Microsoft has also released a press release that highlights some of the new features. Here are some of them
Fast launching of apps from a tile-based Start screen, which replaces the Windows Start menu with a customizable, scalable full-screen view of apps.
Live tiles with notifications, showing always up-to-date information from your apps.
Fluid, natural switching between running apps.
Convenient ability to snap and resize an app to the side of the screen, so you can really multitask using the capabilities of Windows.
Fully touch-optimized browsing, with all the power of hardware-accelerated Internet Explorer 10.
You can find the press release here http://www.microsoft.com/presspass/features/2011/jun11/06-01corporatenews.aspx
If you want to learn about how to build all this new stuff then check out the Build Conference in Anaheim between September 13th and 16th.
BUILD is a new event that shows modern hardware and software developers how to take advantage of the future of Windows. Learn how to work with the all new touch-centric user experience to create fast, fluid, and dynamic applications that leverage the power and flexibility of the core of Windows, used by more than a billion people around the world.More info here: http://www.buildwindows.com/
Finally you can read about what Steven Sinofsky showed at the D conference here: Microsoft Windows President Steven Sinofsky Live at D9