Off course there was something crazy about iPhone. It changed mobile industry entirely and introduced Mobile Application economy with introduction of App Store, where developers can upload their apps and can make money. That created entire new opportunities for mobile application developers. Since it's introduction there are number of versions of iPhone are introduced with exciting features and cool UI display.
Being a mobile application developer I daily work with iOS devices and also other mobile devices here are some points which I feel are very spacial in iPhone.
Very Stable OS and Hardware support
Nice Development tools like Xcode IDE and Simulators
It's not like iPhone is good in all the cases, there are some drawbacks.