* It gets rid of a system cobbled together from init, inittab (which people rarely remember exists), monit, cron, and inetd/xinetd.
* It removes a bunch of horrible hacks in init scripts such as calls to sleep.
* It removes the need for pid files.
* It removes the need for a lot of stupid boilerplate, like the whole start-stop-daemon stuff in scripts.
* It allows precisely tracking what belongs to each service. I can easily find out what a random process belongs to.
* It captures all the log output of each process
* It drastically improves the upgrade process -- I never need to look at a 3-way diff of /etc/init.d/apache2 again
* As a developer it means I don't need to write a slightly different script for every distro
* It makes logging a whole lot pleasant
* It allows having user services without having to hack around it with cron
* It allows a whole bunch of settings to be applied to any random service, without having to edit a shell script and figure out how to stick it in there.
* It means services run identically when started by hand, without the confusion of a service inheriting my local environment.
* It makes my VM servers boot faster. And if you're going to pipe up with "I reboot my servers once a year", that doesn't cut it for me. I boot my servers on demand, when they're needed. They adapt to the load.