Me, too
I've been complaining to Comcast about their interference with iChat traffic for about a year, now. Their telephone support staff know nothing about it. Their email support staff say simply that Comcast does not support iChat. The technicians that visited my house replaced EVERYthing from the curb to the computer. I get VERY good speedtest results - sometimes as high as 20 megabits per second. And yet the problem persists. When I try to videochat from California to my father in Florida or my nephew in Indiana - both Comcast subscribers - we can set our watches by the precise timing with with our sessions work properly. At one minute, things start to degrade, until finally things freeze up completely. Given what I've measured, myself, and what I've seen on CNN and in the papers (AP, one week ago), I am convinced that Comcast is purposely (a) ignoring the problem, or (b) actively causing it, so as to eliminate or reduce the competition to their VOIP product. MANY folks on other forums, both here and elsewhere, are reporting this exact set of symptoms, and also stating that as of one year ago, iChat used to work fine via Comcast's network connections.
The internet should be usage-neutral. Commercial concerns that wont accept that should not be supported by continuing custom from those offended by their practices. I personally cannot wait for a reasonable alternative. I've had DSL, and would not like to have to return to it, but AT&T's U-Verse service, or Verizon's FiOS would suit me fine. As SOON as either of then or something like them becomes available, I will be sending Comcast a letter informing them of my opinions. I urge all affected or concerned others to do likewise.