Author, here. I was just thinking yesterday that it's time to write part II of that piece. But briefly, for the HN crowd: I ended up switching my toolchain to a markdown-based system relying on a combination of pandoc, Makefiles, and various little command-line utilities. Again, this is mainly for large, book-length projects where compilation speed becomes an issue (though I have been using the same system for written lectures all semester).
Pandoc, of course, gives me HTML, EPUB, docx, LaTeX, and plain text. But what I really wanted (for the speed boost) is groff -mom, so I wrote a custom pandoc Writer to make the translation.
I haven't released it, though I'd like to eventually. Pandoc recently changed the way it does Readers and Writers, and I'm not sure I completely understand the new way (right now, it sort of does an "include" on the old-style code).
Delighted to see that the post that inspired this journey is back online. Here's the link again, in case it gets too buried: