Upstart had some really nasty gotchas too, but at least was limited in scope. It'll be interesting to see if we ever move from CentOS to FreeBSD to get away from the horror show that is systemd.
Now read https://news.ycombinator.com/item?id=11550802 and https://news.ycombinator.com/item?id=10357589 . (The mentioned van Smoorenburg rc script has since moved to https://github.com/dun/conman/blob/master/etc/conman.init.in .)
The TrueOS people have replaced Mewburn rc with OpenRC, retaining the FreeBSD init as far as I am aware. I suggested to them back in January 2017 that since OpenRC has s6 integration, they might do well to add s6 to that to gain full service management. I never received a reply. I haven't heard that Laurent Bercot was contacted, either.
* https://news.ycombinator.com/item?id=13458186
* http://www.mail-archive.com/supervision@list.skarnet.org/msg...
I personally use the nosh system and service managers on FreeBSD and TrueOS, of course. I released version 1.34 last week.