Here is an interesting article the The Register where they suggest that Apple is working on an iPhone with a QWERTY keyboard. The say that they have inside sources that Apple actually has a working prototype which they have been showing to carriers. I have no way to agree or dispute this, but find it interesting nonetheless. In short, they argue that QWERTY is requirement for mass penetration of businesses and Apple realizes that they need it if they ever want to gain a large foothold in the enterprise.
The above point is interesting. In my informal experience, I find that people get used to one method or another. I am a QWERTY guy and would not consider the iPhone for that reason although I have heard that you quickly get used to it. I like the tactile feel of buttons which is holding me back. That said, I would be interested in playing with the iPhone for a while and seeing if I really do like it.