Data transfer limit not changed on 50/6 tier service in MN
The new "unlimited" 50Mbps/6Mbps speed tier was announced for availability in the Minneapolis/St. Paul metro area at the beginning of April 2008.
But even though your transfer speeds are roughly 4 times the speed of the next closest speed tier (8Mbps/2Mbps) Comcast only allows the same amount of data to be transfered each month as the 8/2 tier.
And since they refuse to say what the monthly cap is so you can never be sure if you're violating it. But if you can't use your connection for what it's worth then it's certainly not worth paying a premium for.