I have 1Gbps service with them and pay for uncapped. With the cap you can break it three times before they start charging you extra. It's cool to hate Comcast, but it's not an unreasonable system - people who utilize 2TB a month probably should pay more than those who utilize 200GB.
I think uncapped is $50/month, but I've had a friend mention that they were able to get it for $25/month if they leased their modem from Comcast, another $10 a month for a total of $35.