It their flavor of VOIP. It's my personal opinion that VOIP is the future, but not quite ready for prime-time. There are still issues such as E-911, powering, network stability and QoS (quality of service) that are still being resolved.
Price wise, you might want to see what your local phone company is offering in response to those kind of plans. In SBC's area you can now get the All Distance package (unlimited local and long distance in the U.S.), caller id and several custom calling features for the on-line price of $39.99 a month. In order to get this, though, you have to order on-line. See
http://www05.sbc.com/Products_Servic...10-3-0,00.html
If I didn't have kids and a wife at home I might be willing to go this route (actually if I didn't have kids and a wife at home I would probably just cut the cord). However, knowing that this is a lifeline and what I view as an integral part of my family's security, I'm not looking to go this route just yet. As technology improves and matures, I may consider this down the road though.