This, at least in concept, looks like a potential successor to printf() et al. The general accessibility of it is lacking given that it's a C-only API at the moment (there don't appear to be bindings for other languages), and I'm left questioning whether format strings are the best way. Perhaps worse is better in this case.

When thinking about this problem I've not been able to get beyond the decision of "should it be done with something like a builder pattern and a graph of objects/structures" or "should it be done with a DSL" (which is what I consider the format strings approach to be). A DSL is more immediately convenient when creating output, but when you want to understand the structure you're emitting it seems better to have code that is explicit and imperative.