People now view cellphones as a commodity, like coffee or sugar, and now buy them largely based on price concerns. That, and one-third of people no longer use a landline telephone, instead relying solely upon their cellphone. Those are the two big conclusions from a recent comScore survey, both of which seem fairly reasonable. As one of the comScore folks said, people generally see cellphones as being about the same—same so-so quality no matter what model/carrier you go with—so the only major consideration when switching carriers is price. (Though I would imagine power users, people who read sites like CrunchGear, would also think about other things like quality of Internet access and ease of installing applications—precisely why I’m leaning toward an Andoroid when I get a new cellphone this autumn.)
As far as people not using landlines go, yeah, of course. Why would you bother at this point? When I’m home I’m always online, so you can either IM me or call my cellphone. No sense paying Verizon for a landline I’d never use.