I've been using Vonage as my "landline" for years. My dad switched to Magic Jack a couple years ago and loves it. I consider my VOIP my "landline" as it's my main contact number.
I hardly use my cell phone. Mostly have it for emergencies when traveling, as a way for coordinating with members of my traveling party when on the road and using the GPS/internet for directions. Due to a nearby TV tower, my cell reception in my house is horrible - calls constantly drop...although that may just be my provider as friends on other carriers don't have any issues in my home. Planning to switch providers later this year to see if that makes a difference.
Like another poster, I don't feel the need to have people contact me 24x7 - I work in computers and deal with being on-call for work. I have no desire to be "on-call" for my personal life. People can leave a message and I'll call them back at my own convenience.