I really appreciate what PDF can accomplish, but I also really dislike that it turns into a black box. There really ought to be something that can describe a document structure and also describe document layout in a durable and portable manner. In the range of XML/JSON <-> HTML+CSS <-> PDF <-> PS <-> RAW, it really does feel like there's something missing between HTML and PDF.

And it can't be LaTeX, because the document shouldn't be a programming language at all. "The document is a program" has proven itself to be a terrible scheme overall.