The sleek device has turned phone users into mobile web users. And in some big cities, notably New York and San Francisco, AT & T's data network is struggling to keep up.
David Singer, a New York web designer, says his iPhone regularly drops calls. And he says connection to the Internet is a sometime thing. At first, he thought the phone was the problem.
Then he tried it in Seattle. It's like the difference between a cable modem and dial-up, he says.
It was a foreseeable problem, says tech guru Peter Rojas, creator of the blogs Engadget and Gizmodo. AT & T didn't build a big enough network for the demand.
The phone company says it's working on the problem, but it takes time and money.