We only use Comcast as our ISP by default because we couldn't get any of the services we really wanted to connect to our apartment complex. Comcast was our third choice, but only because they pretty much own the area we live in. They work great when they do work, but the service goes down every once in a while, and they're really not that great at getting things going again. We once had three different Comcast guys come out to fix the same problem in one week before they found and fixed the problem, so that was less than impressive.
But like I said, when they work like they're supposed to, we don't have any problems with them.
Oh wait! They're also more expensive than the providers we would have preferred to use if we could. $60 a month definitely adds up, so I wish we could have gone with someone else.