I recently dumped Qwest as my ISP and went with Comcast. I got a free install from them so I could have one of their techs come in and run new cable to my computer "room". When the guy showed up I mentioned that I had a Mac, and he said no problem. He had me running in minutes. Now - he was a third party for Comcast, but he did know his way around a Mac and was quite comfy with it. He was about 19 years old.
We have Time Warner Cable as our ISP, and they are excellent with Mac installs and service, even the people on the phone are Mac friendly, you just ask for someone familiar with Mac and they will transfer you without a hassle.