I'm a Comcast user in northern California. Comcast was actually ordered to cease those specific practices by the FCC in 2008. However the ruling still allowed them to practice bandwidth shaping, and in my personal experience they are still mucking with upload traffic.
In various bandwidth tests with friends and applications I have noticed that my Comcast "up to 2mbps" upload does the following:
1.6 - 2.0 mbps on direct uploads (via IRC) to friends on comcast
0.8 - 1.0 mbps on direct uploads (via IRC) to friends not on comcast
< 0.4 mbps with peer to peer applications, such as bittorrent or the WoW patch client. If my upload speed approaches 0.4 mbps, my entire connection will slow to an unuseable crawl. Also my connection tends to have problems if I am connected to more than 15 peers.
In demigod, I infrequently gets spikes of heavy packet loss. I get dropped from about 2 games per week for this reason. Separate from that problem, my modem (which was delivered new about a month ago due to the previous one dying) also locks up and refuses to send any traffic until I restart it about once a week.
Often times when I'm dropped from a game, I will see a massive spike in packet loss for about 5 - 10 seconds, without full internet connectivity failure. I usually stay connected to IRC and often do not lose my ventrilo connection. My guess would be that Comcast is doing something to interrupt users transmitting p2p data streams, or perhaps users with long sustained uploads to multiple targets, periodically to discourage this sort of use and potentially reduce bandwidth useage.
How can I say for sure this is due to Comcast? Well I can't really, but I can make a guess based upon some pretty strong evidence, i.e. the upload information above coupled with the fact that this didn't happen before I began playing demigod, and it does not happen when I am playing any other games.
Comcast's connection stability and speed have been excellent for me in the past, and I am not a heavy p2p user so the throttling was annoying but not disastrous. And even though it happens infrequently, getting dropped from a partially completed game leaves me extremely frustrated and angry.
For my own general happiness, I've signed up for a new ISP. They're due to install Monday. I suppose I'll find out then if Comcast was the problem or if I need to start looking elsewhere.
