We have had Vonage for almost 3 years now. We don't make a lot of calls but we needed a land line in our home. The cost of the basic service runs $24.99 and with taxes and other charges the total we actually pay each month is a little over $30.00. When you sign up, you get your first month free and when you refer customers to them and they sign up, you get free credits as well.
The service includes free local and long distance calls in the US and Canada and very cheap rates for calling other countries. There are free features such as caller ID, call waiting, and voice mail. Since it works with your computer, you must have broadband Internet connection to use it. Another important thing is when you have it installed you have to fill out a form to your local 911 service to register it somehow so they know where the call is coming from.
For the most part we have been happy with the service. Sometimes I do have a bit of difficulty with our phone line in quality and sound but I don't know if it has to do with the Vontage or the cordless phone. If the Internet connection goes down though or you loose power, you loose your phone too. This would be my number one complaint about the service. We purchased a small battery backup system to use in case of a power outage but that only lasts for about 30 minutes so after that time you are out of luck. For the price and the ability to call anywhere in the country with no additional fees though, I would say I am pleased with the service.