_ Their brand new, modern, open-souce, popular langage : Swift
_ The Cocoa API Design in general.
_ Great Documentation of the Cocoa APi Design guidelines.
_ Mature eco-system of open-source, third-party libraries. Review collected by and hosted on G2.com.
_ The lack of editing features (ex: refactoring, usage search, etc.) XCode provides compared to other IDES (ex: Appcode or Android Studio).
_ The painful and complicated code signing system.
_ The painful and complicated crash symbolicating system.
_ Storyboards, which are mostly just a group of nibs batched together. Horrible when working in multiple teams. Review collected by and hosted on G2.com.
