Microsoft made the Windows 8 developer preview available at the Build conference earlier this week. The opening day keynote session has lots of demos. Windows 8 is a radical departure from previous releases of Windows with its new 'Metro" user interface optimized for touchscreens. Another key area of focus is decreased boot time and the following video of Windows 8 boot in 5 seconds demonstrates this. The developer preview is available to everyone here and Steve Ballmer announced over 500,000 downloads overnight.
I installed Windows 8 developer preview on spare laptop connected to a touchscreen monitor and recorded a brief video of my experience (below). Another video from Winrumors compares the iPad and Windows 8.