Despite what Apple claims
The number one smartphone in the US is not the iPhone, despite what Apple would have you believe. New data from NPD Group suggests that RIM's Blackberry Curve wiped the floor with the kit for for the first quarter of the year, with RIM taking three of the top five spots.
Part of the problem is that the iPhone in the US is no good for business. Since Jobs' Mob decided that it would only sell the rights to one carrier it has been stuck on the mediocre AT&T network which has a fairly spotty performance. It has a reputation of being slow to fix network issues and slow to respond to customer complaints. To make matters worse, Apple's policy of locking in its phones to AT&T often turn machines that people have paid for in to expensive bricks is exactly the sort of behaviour businesses can't tolerate.
That might change if Verizon gets the chance to sell the iPhone but right now Apple growth against RIM is frozen because of its control obsession. In the meantime do not believe Apple fanboys or Apple marketing which claims that the iPhone is the number one selling smart phone in the US. It simply isn't and they only have Steve Jobs to blame.