There are several excellent features offered by Internet phone services, but the most valuable one is easily the ability to keep your number unchanged even if you change your address (in my case, this was the clincher). Voice mail messages delivered via email is feature that we have found to be very useful as well among other features.
On the downside there are 911 call issues. In other words, the Public Safety Answering Point (PSAP) doesn’t automatically know your details when you make a 911 call unlike a conventional phone line. Depending on your physical address this might not be an issue for some Internet phone service providers because of the Enhanced 911 (E911) services.
Vonage is a well known provider of Internet phone service. They had a recent IPO. Packet8 is another option. However, I chose Lingo since they offer unlimited calling to Western Europe in addition to US and Canada. With Skype offering free calls in the US, these services are soon going to get a run for their money.