Download and more reference material here:
Great crash course article from Alexandra Rusina here:
Basically you get two new powerful C# language keywords, await and async. Instead of having to write callback methods for multithreaded code, you can now decorate a method signature with async and call the method with await. You write the code as if it were a synchronous block of code and let the runtime perform the heavy lifting. Very cool and really streamlined. I wonder what debugging will look like.