I switched to Vonage at home over DSL just to save US$ over Qwest. Vonage is not bad, but audio quality suffers slightly if you have a son that games and a daughter that shops iTunes. I am satisfied especially saving over US$40 per month and I am not disappointed with audio quality overall. Note the 911 issues in the press of late, however.
Their customer "service" sucks. Plan to spend some time dealing with slow learners to get your account set up and activated. Do not anticipate replies to any emails you send and God forbid, you should get an answer to an actual mailed letter with questions to the CEO.
Now I am not high maintanace, but I was looking into getting my 6 business lines changed over. It has been many months with no responses and it is very obvious that Vonage is great at the home level of you-get-what-you-pay-for service. They cannot cope with anthing else at this point.
Just don't expect answers to your questions.
Could be worse, could be Cingular ...