The major issue people are concerned about is that things will be built on top of systemd (and they have been built on top of systemd), and then you have a huge unrelated dependency on this init system which makes it hard to swap out in the future if you want to use containers.
I have been running Fedora before systemd (2010) was introduced and have never had an issue with it. I am now running Fedora 25 without any issues. Since my OS is on an SSD I can power up then login in then start my applications within less than one minute.
Just for you I started up my systemd configuration GUI and you can for "Units" and "User Units" see the following "Load State", "Active State", "Unit State" and "Unit". If I want I can "stat", "stop", "restart" and "reload" a unit as well as being able to "edit" and "isolate" a unit. There are plenty of other options available for you but I would suggest reading up on them.
Basically screwing up in systemd is pretty much the same as screwing up in an init system and instead of whinging about it, fix it.