1. Not really. Most sysadmins have a decent template init file sitting around or you just steal another one on the machine and modify it. They are also more flexible as some startup processes aren't quite as simple as systemd thinks (consider lockfiles, temp data purging, permissions etc).
2. ulimit / selinux - per process. cgroup whilst funky looking is YET ANOTHER disposable mechanism which will no doubt get canned in 5 years like ipchains ipfwadm etc.
3. service --status-all
4. Concurrent startup yes. That really doesn't make much difference on a server with large IO and CPU capacity.
2. cgroups can do way more things than ulimit.
4. Have not used enoug containers to know how much it matters in practice.