I love F#, and greatly prefer it to C# for most tasks, but I think you're overreaching a bit. C#'s dynamic feature is also extensible (via IDynamicMetaObjectProvider) and much more complete than F#'s (e.g. F# probably ought to have (?[]) and (?[]<-) operators for dynamic indexed properties). Likewise, there are several real benefits to having built-in support for async/await, such as the improved performance of a state-machine-based approach and a far better debugging story (e.g. call stacks that are async-aware).

C# is truly a great language; it was just created by people who have different priorities than you (or I) do.