I'm not about to get involved in the larger debate about torrents here. As a technology, it is certainly an interesting thing, though I tend to find them slower to deliver files. I have Bittorrent installed on my machine because some programs that I've downloaded in the past were only distributing their files that way -- I find that annoying, since torrents are never personally my first choice, but I know no-one here was advocating that.
Arcen doesn't pay for bandwidth in any fashion, not for our site, and definitely not for our various mirrors. The mirrors tend to make money based on their ad revenue, so far as I know. In terms of the costs of our own site, we pay a flat yearly fee at present. In the last few months we were using something like 300GB of transfer a month despite the mirrors taking the vast bulk of the load, so I'm having to figure out a way to offload that more.
The patch updates in particular are something that I need to start hosting on a different FTP source -- FileFront has a service that looks excellent for game developers, but I have emailed them twice and have gotten no response. Anyone else know of a free FTP hosting service that allows for direct http or ftp downloads, and which doesn't charge for usage? I imagine those are pretty rare, but they do exist (see Filefront). I publish game updates via the AppLife tool, which uses FTP to do the publishing, and then AI War downloads these updates based on the HTTP protocol. So I'd need something that is compatible with those two requirements.
Other than that, bandwidth has not been a particular concern from my end of things. For md5 hashes, that's something I'm not familiar with how to create (I'm sure I could google it), and it's not something that seems terribly common with... anything I've ever downloaded aside from torrent stuff. I might get into that at some point, but it's not like I'm looking for new things to make releases slower.