Yeah, C#'s async is a weak version of F#'s workflows, but with a single hard-coded implementation. Research (Haskell) and other languages filter into F# (and team), which filters into C#. F# has had async workflows since 2007.

LINQ's another example of a place where the C# team sighted one end advantage (queries) and implemented the minimum to make it work. That's why all the features around the main LINQ part are half-assed (limited expression trees, ambiguous lambda syntax, very limited type inference.)

Overall, C#'s a nice enough language for a lot of projects. The tooling really helps sells it, too. It's just rather verbose and limiting, unnecessarily. I just can't think of any place where C# the language is significantly better than F#.

But, if you're ranking it against the likes of Java, then yes, C# is close to perfect.

Edit: C# implements a lot of stuff right into the compiler, things that'd be useful more generically. For instance, foreach and collection initializers use duck typing that's baked into the C# compiler. That's a generally useful feature, but again, hard coded for a specific scenario. F# has some of that too, but not to the same extent (F# warts arise mainly when you push the edge of F#-C#ish interop).