Part of Paul's reasoning depends on Apps being central to the iPhone experience the same way software is central to the desktop experience. I'm not totally sure this is the case. While apps are certainly a major component to the iPhone, are they really the major factor in end-user adoption? With the exception of games, how many killer iPhone apps are there that don't already ship with the phone? The phone shipped for…
The OS bundled ones are the ones people use the most. Across the board.
If I had to guess, I'd say third party apps are just as often or more used on iPhone than on, say, Windows and Mac OS X. Simply because, on iPhone, a lot of web apps out there are used via a special-purpose iPhone app rather than the web interface.