I need to create a daily full backup (snapshot) of a directory tree + hourly differentials. A developer who has only sftp access needs to be able to restore from the backups and hence a solution such as rdiff-backup or duplicity wont work as she would need shell access to restore (afaik). I imagine that rsync and cron would do the job well. What is the best solution?
Sounds like you want some kind of snapshots. If you are using ZFS you will more or less get that for free. Otherwise you can kind of "fake" it using rsync, hard links, etc. Rsnapshot provides a good solution for that.