I think Apple's foundational technologies have been fantastically stable since OS X came along. It's been pretty much the same solid core since 2001, from OS X

I think Apple's foundational technologies have been fantastically stable since OS X came along. It's been pretty much the same solid core since 2001, from OS X 10.1 through iOS 6. The only major piece to go away was Carbon, which was pretty much just for OS 9 backwards compatibility to begin with. I use many of the same classes and techniques in iOS today that I did in the very beginning of learning OS X programming.