DISCLAIMER: THIS CODE REVIEW IS A LONG WORK IN PROGRESS, I COULD BE COMPLETELY WRONG IN ANYTHING I SAY.
To do a proper code review, you need to understand the purpose of the code, what all the stakeholders want. From my own perspective, init scripts work fine, but since Unix companies keep trying to create new init systems, they must have different needs than I do.
Here's a list of the stakeholders. I need to figure out what their goals are.
1) System admins.
2) Desktop users.
3) Distro builders.
5) Android (if systemd turns out to be good enough).
My suspicion is that systemd has taken over because it makes things easier for 3.
At its core, Unix is a system for programmers. What other system comes with a compiler and multiple interpreters by default? Bash is so much more useable than DOS, or even powershell (yeah, go ahead and flame me but I'm right, Powershell doesn't even have < working). Unix was designed by programmers and for programmers.
The reason I'm talking about it is the traditional init process is incredibly discoverable. All you have to do is look in the /etc/rc directories, and you can figure out how your system boots. You can see it all. For a programmer it's easy. Poking around in the system to understand it is one thing that makes Unix great (and what I like about Slackware: the whole thing is lovingly crafted).
So that describes the approach I am taking to code review, and to the init process. Hopefully Systemd is an improvement.