The weakness of the type system becomes a problem pretty quickly - simply having a different implementation of an adaptor, be it per language, transport or even simply type of node makes for an endlessly leaking abstraction.

That's what I felt that overlapped with the GP's comments on composing complexity. It's not so much that you _can't_ implement multiple cases (not to the nth degree, just a handful), it's that the abstraction leaks painfully.