What made me hate upstart was that it still is willing to get the default runlevel from /etc/inittab, but it doesn't bother to emit warnings to the user that the rest of /etc/inittab is completely ignored, at least on the version of CentOS I was using. I think it's particularly user-hostile design for any program to accept configuration that does nothing (excepting whatever comment syntax a particular config file uses.)

I would vastly prefer if it either made lots of complaints about the ignored lines in inittab, or even if it it failed hard -- because then I would have to fix the problem immediately.

I have used systemd, but never actually poked around at its configuration (having just run Debian with it as a desktop user), so I can't properly judge it yet.