The biggest "feature" is the touch and multi-touch integration, which takes many of its roots from Microsoft's Surface Table, and will be available as an interface options for other apps. Here's some more stuff they pulled out, which we captured in photos here.
• There will be a OSX-like dock, though how OS X-like is yet to be seen.
• Multi-touch gestures in photogalleries like two-finger zoom, flicking, and panning. Think of the photo app on the Microsoft Surface table.
• Multi-touch paint program where you can draw with 10 fingers (again, think of what you've already seen in Surface)
• Multi-touch piano app
• In-depth mapping application that pulls from Microsoft's Live Maps and Microsoft Virtual Earth
So, in reality..maybe 3-4 years?