Windows 8, actually.
The North American TechEd videos are online now. The keynote from Day 2 is about Windows 8 and is worth watching.
Actually, whilst watching the day 2 keynote see if you can count the times “actually” is used, actually 
I guess it’s better than “So…”
Biggest moment of irony in the video is when the desktop is demo’ed with windows docked to 50% of the screen. It’s a real pity you can’t window a Windows RT app to do the same.