Also, given http://skarnet.org/software/sdnotify-wrapper.c it becomes possible to both use s6's superior notification approach in code and to be compatible with how systemd handles notifications.

This is exciting to me and I would like to encourage you to make it way more obvious, given I've been playing with s6 for a while and still only managed to notice it existed because of http://homepage.ntlworld.com./jonathan.deboynepollard/FGA/un... - and while perhaps that's due to my own stupidity, likely there will be other similarly stupid people who'd also value this information ;)