As for the second point, that's what Accept header is for. And I personally never had much trouble in Go with deserializing all those "weird response types" but it may depend on one's coding style.

> I have to say that at least for generic APIs with many differing clients, the idiosyncrasies of typed-language clients would not rank too highly on my list of design considerations

Hey, would you like to consume an exchange format that has meaningful distinction between strings and atoms? Those come from the dynamically-typed languages area!