A big advantage of jigdo is it allows the user to use a local mirror to fetch the rpm's etc. that are on the iso's - without the local mirror needing to host iso files.
The torrent works well for fetching fedora - and should certainly remain as a distribution option, but many people can not use torrent because of firewall issues or company/school policy. Since jigdo uses ftp/http and does not open ports for serving, that's not an issue.
I don't know of jigdo works with DVD images, but by the time a mirror has packages, src packages, cd images, dvd images, that's a LOT of space it needs and it just seems that a smarter solution would be something like jigdo.
Just my opinion - it works exceptionally well for Debian.
