In this blogpost by The Unofficial Apple Weblog, they write that the iPhone won't allow user applications. While the interface looks and feels like Mac OSX, it's an OSX designed specifically for the iPhone and there won't be an API or programming envrionment provided by Apple.
Also on the bad news train is the fact that the iPhone can only sync through the dock/cable connection. No syncing with your computer through WiFi. Hopefully you can still transfer and stream media back and forth without a cable connection, but that remains to be seen.
The no user apps is a pretty big blow though. With the awesome interface and beautiful screen, there are a lot of great interactive applications that could be created for the iPhone. Apple has effectively shut down any form of experimentation now from the enthusiast community and that's pretty crappy. Though it's not that surprising considering the iPod is locked down pretty tightly as well. But man, imagine a customized Wikipedia or ProductWiki interface for the iPhone, similar to Google maps, instead of just webpage rendering.
