I have an iPhone, and it's a useful tool. I have 100 free minutes and 40 free SMS a month, I may get close to the minutes but I hardly ever send SMS around.
It's mostly in silent mode anyway, real people always have priority over phonecalls except perhaps if I'm expecting an important call or my boss is calling but neither happens often.
It has actually made some situations easier and more convenient due to the internet flatrate and connectivity, which is the main reason I bought it. I can check the mails, read the news, check webpages, chat etc. all on the move and wherever it has an internet connection, or I cannot, it's my choice, there's no force and I turned a lot of the notification things off.
One of the more useful things is that I can send messages etc. over the internet, there are apps doing that which make SMS useless if the other person has an iPhone, too, like someone I know from Switzerland, I can stroll through a park and send her a picture of the park for free etc. Maybe it's not especially useful per se, but it's pretty nice, like wearing nice shoes that cost 50 bucks more than just useful shoes, or a nice suit that cost a thousand bucks more than just cheap jeans, a shirt and sandals.