Not sure if anyone else has used this service or not, but I use Vonage for my phone service. I have had absolutely no issues with it at all in regards to the phone calls. The only problem I have had is trying to fax with it... but I eliminated that by switching to efax. I pay $24.99/month and that includes unlimited long distance. Best deal out there, in my opinion!
The only catch with Vonage is that you have to have high speed internet to use it... but if someone already has that, and needs unlimited long distance phone service, Vonage is the way to go!
I think the telephone service is area specific. I use vonage in CT and they are horrible. Comcast in MD is a great, as if Verizon, but Comcast in select areas in PA and VA are horrible.