I never owned a mobile phone because for one I never really had a need for one and then we live 6 months in the US and 6 months in Europe - so I would have needed 2 systems for which I would need 2 different plans.
But now I use the N7 for making calls - with GrooveIP. Free in the US and from Europe to the US. 2 cents per minute from the US to Europe. That is a real money saver for all the overseas calls we make all the time.
Another highlight is the GPS. It navigated us out of Orlando last week without any problems -- else we would probably still be roaming the Orlando landscape.