I'm a professional sysadmin. Scope is important so we'll go by cores. The total number that I admin and/or work directly with total over 100,000. I work very closely with a lot of cutting edge technology. [FQ]DR IB, distributed fs in or near the range of petabytes, openstack, clusterware. We do this to run systems geared towards bioinformatics, CFD, CAE, etc. I can't speak for everyone but if I included a few colleagues I work with closely, the number of systems grow astronomically as they may have detailed knowledge of much bigger systems than I do. None of these systems will touch systemd with a 10ft pole.
I use systemd on one system, a personal laptop that I use linux mint on for steam. Due to some configuration I had no part of, this laptop will take about 4 minutes to boot depending on the network I'm on and say "waiting 60 seconds for network" even though it's a static ip set outside of nm. I live in CLI 24/7, I never use the gui, and I don't even want to bother with this. Why? Because it doesn't make sense from a "sysadmin" point of view. I'll jump into things for work that I have no clue about and that is what I love about my job. But what I've seen of systemd from my own experience and those of my colleagues (not from reading slashdot), the things I'd be working out are not real problems but rather retarded defaults set by systemd that assume things it shouldn't. It's very invasive and overreaching and that's NEVER a fun thing to work with from a sysadmin point of view.
Systemd isn't the worst. I don't like it but I see that as a personal preference and if it ever got its shit together, I could see it being a boon for workstations or laptops. But in no way, will any real sysadmins who do REAL work with linux under the hood come near systemd anytime soon. RHEL7 adoption is going to be a joke.