I am happy to see articles on Cocoa programming for programmers at any level of expertise. Good job! I know people have day jobs that don't involve programming and nevertheless want to learn Cocoa. I think that is great!
I just don't think it is wise to minimize the importance of learning to program in C before attempting serious use of Cocoa. An understanding of C and low level programming issues is important before attempting any serious programming project with or without Cocoa. Frankly, learning everything there is to know about C and the most common standard libraries used with C will take a tiny fraction of the time needed to learn to use Cocoa effectively. I fear that attempting Cocoa without understanding C and low level programming issues in general is going to be frustrating and error prone. Furthermore, a general understanding of computer science is needed even for hobbyists programmers. If this series teaches enough general programming skills and enough C to really use and understand Cocoa, this will be a great series! If not, I worry that people will end up discouraged and won't understand why their programs are slow and buggy.
I hope my concerns are misplaced. I am sure we can all agree that Cocoa is a powerful tool. It is sometimes necessary to learn how to use less powerful tools before the more powerful ones can be used effectively. Impatience aside, I recommend that people really learn C before attempting Objective-C and Cocoa. C is a valuable skill and contributes a foundation of knowledge that is applicable to almost any programming from LISP to C++ to Java to perl.