I think it depends on your lifestyle, whether you live in an urban or rural area, and your need to contact others. I have found that most of our need for long distance has gone away, and most of the remaining can be done with Skype. For us that's a consideration since connect time adds up if you're talking to a relative across the country or the planet.

We have considered doing it at our summer home, since all three of us now have cellphones, but I keep the land line in this rural area so that local contractors and neighbours can reach us easily, and so that I can use dialup internet. But this may all change, if I get a 3G phone--we have good connectivity and David already has an iphone, so the need to read mail and do a little surfing goes away.

Here in the city, my son is cellular only. He is nomadic and rarely home so it is a reliable way to keep in touch.

One factor can be whether you can find a cellular plan that includes free talking to a group of family or friends. For example my son and I share a plan so we can talk to each other freely at any time. Unlimited texting also helps.