As far as essential features go, you need to use the right tool for the job.
If your data set is small and fits on a single volume, use rsnapshot or rdiff-backup. Both offer incremental backup, are very space efficient, and are really easy to use.
For larger or more sophisticated backups that have an offline component I use Bacula, it takes a while to setup properly, but it's rock solid and has quite a few features. I recommend coupling it with a web interface like webacula.
One good idea btw, for every server I have I use rdiff-backup to keep a daily incremental backup of /etc in /var/backups/, it costs you nothing and will save you a lot of headaches if you can't figure out why that last change to a config file is causing so much havoc.