Having worked in a few languages over the years, all with different ideas of concurrency, the C# system is one of the nicest.

It's a bit tough to get your head around, but it does a good job of keeping code readable while correctly blocking and descheduling threads.

A lot of developers get async wrong, so anything to help get it right is a plus.

Personally I prefer the F# async system, but it's harder for a curly-brace developer to learn F# than a new C# keyword.