My overall reaction similar to what I said based on textual reports. Jobs saying that web-based applications are as good as native ones on the iPhone is a big change for him, and a sign that development really has changed. What was clearly flawed in the iPhone directory app demo was the need to write all the integration links into the site - how about Safari/iPhone natively understanding hCard and integrating it with apps, like Operator does in Firefox?
Stacks seems not to really solve the too many documents problem well - see Tim Oren's discussion of literalism and magic (Tim worked on 'Piles', the less euphoniously named version of this idea at Apple, long ago).
The dynamic DNS support integrated in 'Back to my Mac' is great idea for those not yet committed to keeping their documents in the cloud. The tension between Jobs advocating a new OS with 300 features, versus a thin client on the iPhone to the same developers was pretty clear.
Jobs saying that Safari for Windows has built-in support for both Google and Yahoo Search was not something I saw anyone pick up on.
Oh, and one more thing... the new iChat features look great, but why is there still no demo or even mention of iChat on iPhone? The main thing I use my sidekick for is AIM chatting, and if iPhone can't do that and forces chat through the procrustean constraints of SMS it's a huge missed opportunity.