I'm unable to give any technical input regarding systemd as I don't know much about init systems. Here are a few links that might be useful:

http://without-systemd.org/wiki/index.ph...st_systemd
https://suckless.org/sucks/systemd/

One thing I've noticed is how different distros handle systemd services. For example when installing mpd on Arch you will be required to enable the service manually whereas on Debian it will enable it automatically. I'm personally in favour of manually enabling/starting services but in Debian's defense at times it's very convenient. The problem with this for me is that it assumes you want the service running at startup, which is reasonable in most cases but not all. Another problem is that by default the program you just installed could've pulled in some other services such as avahi, and now they're also enabled. I guess that's not really a problem with systemd but how different distros incorporate it.

Systemd unit files are stored in sub-folders, which is a nice way to organize things but it could confuse some users. For a user having service scripts in either /etc/rc.d, /etc/init.d, or /etc/sv is much more straightforward.