Ours has been spotty today, and was also spotty one day last week. Spotty meaning I can take one call, hang up the phone, and not have a dial tone and 30 minutes later we are back in business. It's odd and annoying. We have Comcast for internet, phone and cable, and if one is out, another usually accompanies it. Last week we had no cable or phone, but the internet was fine. Today - cable, but not phone or internet. Usually the clarity is great though.
We did have problems initially (but that was b/c of our connection coming into the house which it took 4 or 5 service calls to diagnose). If you do have trouble, just keep harassing them. If you find a service guy you like, ask for his contractor number so you can request him in case other issues arise.