One of the bigger arguments is also "it only works on Linux, what about BSDs, OS X, etc.?"
In what way is that a "big argument"? BSD has their own rc-thing (not sysv init), OS X has launchd (not sysv init, shares many similarities with systemd actually, such as socket activation), Solaris has SMF (again, not sysv init), etc.
Apart from a bunch of non-mainstream Linux distros sticking with sysv init, who else is actually using it?
* https://news.ycombinator.com/item?id=11415985
But yes.