I have to disagree.
Steve talked about the iPhone interfacing with other online services like Yahoo and Google. Don't you think Apple will have an incredible tie-in to .Mac besting the services from Google and Yahoo? Why would they sell a phone that works with other services better than their own? This will sell more .Mac subscription services with just a relatively small amount of work.
Steve also talked about the iPhone integrating with a couple specific Microsoft applications as well as Microsoft Exchange Server (albeit, probably limited). Don't you think Apple will integrate the iPhone with Leopard to a greater degree than they will be with Microsoft Windows? You better believe it.
So there are 2 potentially impressive features, unannounced at this point: integration with .Mac services, which will increase the value of each product individually as a result AND integration with Leopard.
One other thing that no one has mentioned — since I am posting I figure what better place to bring it up than here. Apple has said that the iPhone will have internet access via wi-fi as well as through Cingular's 2.5G data service. But what is to promote and entice people to sign up for Cingular's data service?
Well, I will tell you! OK, I'm not in the know so I cannot say this with 100% certainty, BUT...
For those that don't have a computer in order to purchase music from iTS or for those that want to be able to purchase music from iTS while mobile and out on the town cavorting with friends, Apple will provide the iPhone with a version of iTunes. This iPhone version of iTunes (just like the desktop version) requires access to the internet but the access must be through iTunes. It cannot be through a browser; therefore, the use will be restricted to Cingular's paid data service. Doesn't it make sense that Apple will have a version of iTunes on the iPhone that uses Cingular's data service. This would make Cingular very happy.
And certain tie-ins with Apple's .Mac service might be provided in this same manner — making Apple money and Cingular too.
But this is just logical speculation that has not yet been... speculated on... or announced.