Given a torrent tracker you can track the number of downloads that have been completed and the number of downloads still ongoing, as well as the number of seeds available. Two days ago, a single machine at the office started hosting a seed for the latest Fedora Unity Re-Spin, and it spits out data at 4 Mbps average, with only 8 (!) complete downloads, and while 4 other seeds have joined the swarm (and I'm still swamping the internet connection).

That is so much different from the Jigdo concept. Per mirror, we do an estimate 277 GB per month. Would we have been using Torrent, that would have been equal to 69 completed transfers. Using Jigdo however it equals to an estimate 1300 downloads (per mirror). Again in torrent that would be 5.2 TB for each of our mirrors to transfer. Can you imagine we seed that from our home or even office internet connections?