I'd like to point out that this is a good time to really test your connection. I've never downloaded anything faster than a torrent of a fresh ubuntu release.
I wonder whether there'd be major security concerns if a torrent layer was stuck over the main centralized backbone? It could probably reduce bandwidth costs for hosting and provide better speeds to people, though keeping the "swarm" updated might be kind of tricky.
The problem with torrents is they don't work well for lots and lots of (relatively) small "file groups" where each user has a lot of the files, but each user has completely different files. Something based on tiger tree hashing or some other mechanism like that might be more suitable, perhaps?
Perhaps even setting up each already-existing mirror as its own seed-center would help - there are plenty of them around, and by definition they all have the same data. Worst case you end up getting only one connection, and you have the same performance as now, but in the best case you can download from multiple locations at once and get some rudimentary load balancing.
I'm "live updating" right now, and the time estimates jump between 2 hours and four days depending (I believe, given the stability of my schools internet connection) on the load on the ubuntu repositories.
I BitTorrented the 64-bit Desktop edition it as soon as OMGUbuntu broke the news on Twitter and it took me around half an hour (for 700 MiB).