I've been wondering these past few days whether the iPhone's huge array of applications will be THE driving force for it. Or, on the other side, whether the seeming dearth of them for the Blackberry might keep folks away. Will the average user be satisfied with a few key apps, or will they be swayed by the masses available for the iPhone? I'm not sure, myself. The main things keeping me away from the iPhone are the lack of a keyboard (I'm just not convinced that the touchscreen is that grand - know too many people who hate it) and not being able to swap out the battery.
For those put off by the price, here's an option for you: the Peek. A pretty basic device, but should really help move people into the mobile email space. If they allow apps to be developed it would be a solid game changer. We'll see.