If you are a long time iPhone user who is used to its on-screen virtual
keyboard, you might find the need of a physical keyboard unnecessary.
However, some folks insist that its one of deal breakers. We had already some hacks which have paired an external keyboard with the iPhone.
Folks at Crave have actually pitted the iPhone with its software-based QWERTY keyboard against a Netbook with its full Qwerty keyboard (but with tiny keys) to find out which one is better in terms of mobile productivity.