It took 4 of Comcasts contractor technician visits to my house to fix a bad coax running to the building. The first tech identified the problem and said another would come to fix it, and no one did. The next two were completely useless beyond checking that the modem connected, and wasting my time.

Aside from that my 300Mbps service frequently tops out at 30Mbps, seemingly whenever I want to download something large. The upstream bandwidth they offer is also abysmal.