It has been a long wait, but the final version of the iPhone SDK has turned out beautifully, like the new iPhone 2.0 operating system, which will be available in early July—free for iPhone users, and US$9.95 for iPod touch users. They have added key features for both end users and developers, like Office document compatibility, bulk delete and move, save images from email, and notification services for applications that require it, like instant messaging.
They have solved notification without resorting to background processing by adding Push Notification services, which save battery life and solves performance issues. The notification service works over the wireless and the mobile networks.
For users, they have added contacts search, iWork document support including keynote, MS Office documents (Word, Excel, and PowerPoint, likely in the same way Mac OS X does it,) email bulk delete and move, image saving from email, the much-anticipated scientific calculator (for those people with pocket protectors) which automatically turns on landscape mode, parental controls.
They have also expanded the international language support, as expected, adding many latin language plus two forms of Japanese and two forms of Chinese, with finger-based drawing of characters.
Enterprise users will also be able create and distribute apps on their own intranet with authorised iPhones. The apps will only work on those iPhones, and they're synced via iTunes.