I sometimes find it hard to believe that Comcast is a nation wide company. I've had problems with their service and their support, but I still use them as my primary source. But, this is only because of the lack of competition in the cable industry. Where I live, there are two cable providers, Comcast and TimeWarner. But, the bastards divide the area in half so you don't have the ability to select one over the other. Really pisses me off. One of these days I'm gonna see if dsl is better.
As for modem, I suggest you purchase (one that doesn't get hot and lacks fault tolerance) you're own (a good one) and not use one provided by Comcast.