F# -- where has our Roslyn been?

The big thing about the new Roslyn CTP is that it's a C# compiler built in C#, so accessible simply from C# code via a standardized set of APIs; including ones that permit parse tree rewriting (and hence DIY language extensions) as well as giving a more official mechanism for such things as source-level inspection (e.g. StyleCop). Indeed, the lack of any such managed language service for VB is a reason that there's no StyleCop equivalent for the other major managed language.

F# has had the managed compiler from the start -- but presumably (as I've not noticed anything being done with it by way of meta-programming or suggesting coding conventions in the manner of StyleCop) not the suitable APIs. There is a project or several here for someone to take up.