Here's a follow-up from Comcast's CTO, Tony Werner.
"It's really important to us that we make crystal clear that, in contrast to some other providers, we are not prioritizing our transmission of Xfinity TV content to the Xbox (as some have speculated). While DSCP markings can be used to assign traffic different priority levels, that is not their only application — and that is not what they are being used for here."
http://blog.comcast.com/2012/05/the-facts-about-xfinity-tv-and-xbox-360-comcast-is-not-prioritizing.htmlSo there you have it, from the horse's mouth, so to speak. Comcast is NOT prioritizing packets.