When launchd scans a folder, or a job is submitted with launchctl, it depends on a properly formatted plist file that describes the job to be run. This is, for most sysadmins, is the most difficult area of launchd to grasp. SystemStarter used simple shell scripts to launch daemons. launchd requires the admin to be able to properly format an XML file and while not exceedingly difficult, it can be confusing.