This is what sparked my interest in F# originally, and I love it. For the first time ever I'm willing to write async code regularly in C#. I can't wait for something like this to make its way to python (for twisted) or JavaScript (for node).
http://news.ycombinator.com/item?id=3051142
Perhaps it would be interesting to see how it was done in Twisted: http://http://twistedmatrix.com/documents/current/api/twiste...
We'd like to think that the C# guys were looking our way when they came up with async/await, but there's no proof. :3