One thing that I found confusing about writing mac apps was the vestiges of the old memory models. When I started a new project I just clicked the checkbox for Automatic Reference Counting and assumed I was coding in something like Java. I didn't think about memory management anymore.

I remember having to add annotations to the auto generated getter/setters to inform old memory management systems how to treat things returned from the methods (I'm sure I stated that incorrectly but it has been a while). Bottom line is that it was hard to know what was no longer required when coding with the latest release. If I read tutorials that were a few years old they would confuse me with aspects of memory management.