Well, lately i have been playing with RSYNC, and by the time i realize i want to do something different the whole centos mirror is moved to my local server
I also have 2 room mates that download all kinds of stuff.
host a site or two for a few friends too.
The router is mikrotik with 2 wan interfaces 1 lan. Default route goes out cable, With failover if it can't ping a server out on the internet. I have a few things static routed out the u-verse just because they just run all day and use bandwidth (rsync) and i run a large amount of voip on the cable line. I then have one VM that runs torrents and a download manager. Its src ip gets routing marked coming in the lan, and gets out a seprate default route that is ECMP to both lines. I have found that downloads which come from the same place, Like a few linux iso's only like to use one line. But if it is rapid share, where the ip is alot different on each link load balance nicely. And the torrents work well since its many many connections to many different ip's. Between both connections torrents and some rapidshare stuff can hit 33Mb/s down. I would say that monthly I move about 200-400gb of Legitimate traffic. Like my 2 download happy room mates and the other people that check there myspaces every 10 seconds. A decent amount of off site backup too.