I had Vonage for two months. My son still has it. The sound quality is fine. The problem I had with it was number portability and the fact that they lied to me when they said I could keep my existing phone number. After two months of them telling me that it takes time to transfer numbers, they finally admitted that they did not have access to my existing number and that they knew that all along. I don't like being lied to.
most voip carries still have to deal with traditional pstn providers when porting numbers. the problems is that noot all mabell companies have access to every ratecenter. PSTN to PSTN porting takes like two days because the fcc mandates it. When transfering to voip service there is no mandate so everybody takes their sweet time.
I'm in month number 2 and rather enjoy it, in 9 days we are over 500 minutes. Very hew problems or quality issues.
I have a friend that works for 8X8 who does VoIP service under the company name Packet 8. I think it's worth it if you are always going to have boadband internet. Remember if the power goes out so does your internet and therefore so does your phone service.
What's cool is that you can take your little voip box anywhere in the world where there is a broadband connection and it works exactly the same as if you were at home.
tried mine at work and the firewall was to tight or the ports were closed