I used to have Comcast and they were indeed awful. Terrible customer service, frequently clueless and unhelpful techs, and the service wasn't all that great either. Just trying to show that I'm not a complete corporate shill....
Anyway, I know that AT&T and Verizon aren't always liked either, but I think there's some substantial variation within the industry, even if maybe it's only between "awful" and "less bad".