I never wrote native iPhone applications through official SDK. But I played around with unlocked, jailbroken version with unofficial SDKs and frameworks.
While I still believe that there is a huge market for both official and unofficial apps (Cydia and Installer are doing pretty good even after AppStore launch), I'm more interested in the third area of developing for iPhone, that is iPhone Web applications.
Speaking of this, I wondering, how possible is to get an iPhone location (authorised by a user, of course ;) through the Safari call to the remote site? While there is an obvious security issue here, it still interesting to accomplish.