If I were to guess [wrongly, it turns out], I'd say grokking Interface Builder (or whatever it's called now that it's in Xcode) might have been the issue.

IB seems to be a stumbling block, given how many Mac development newbies post to mailing lists asking how to avoid using it to build interfaces.

Maybe because it doesn't generate code? And sometimes people have difficulty working out how their code relates to the objects in IB, and how you connect the two, and how the objects in a nib communicate to objects in other nibs.

Hell, I've been using IB and Objective-C since 1992, and am still figuring out the new Xcode 4 IB.