I've been working on the infernals as the next PDF document. I know I had listed that as something like Project #5, but it looked like something I could do quickly, with not as much rewriting or layout hassles as some of the other projects. I think Ranks of the Undead will be the next one after this, so there's also another factor: a couple sections I wrote for the infernals document will be reusable in Ranks of the Undead, so working on those in sequence should go pretty quickly.
One of the interesting developments has to do with my standard ways of writing monster stats. You may recall that I like doing a header line with a quick appearance/behavior summary in parentheses, like: "Manticore (Fantastic Predatory Beast)" or "Banshee (Vengeful Spirit)". I try to fit in as many as many important details as I can ("Invisible Fiery Sadistic Ursine",) but for things like demons and devils, even my stripped-down versions, there may just be too many of these to be practical.
But then I realized that, since all demons would share some features, all devils would share some features, and so on for each infernal variety, I could have a section header that could define each variety. Like: "Demonic (Chaotic Hostile Destructive Ethereal Monstrosity)". And each demon could then be like "Bat Demon (Flying Demonic Beast)". Basically, it's a macro. I don't have to repeat the terms that apply to all Demonic creatures, because the label "Demonic" stands for and expands to the other labels.
One final note: I might change it again, but currently, I'm going with the original name of the series, "Our Infernal Neighbors", as the name of this PDF.