There is no need to revert to using earlier versions of Xcode to complete the exercises in the first edition Objective-C Programming. While it’s true that there have been a few additions to the language since that book was published (NSNumber, NSDictionary and NSArray literals, @YES and @NO literals, NSDictionary and NSArray subscripting) these are merely ‘shorthand’ ways of accomplishing what is presented in the book.
I’ve recently been racing through a number of introductory Objective-C books in order to provide a recommendation to a friend who would like to start learning the language and, as far as I can recall, the only exercise that will cause an issue is the Challenge at the end of Chapter 15 (this is due to the fact that the words in the proper names dictionary are now incorporated in the standard words dictionary). Otherwise you will find that everything will compile and run on Mavericks using Xcode 5.0 without complaint.
When you state “the <!> error right away” do you mean the warning signs that sometimes appear in the gutter? You will find with Xcode that the majority of these errors disappear as you complete the section of code that you are working on (if you click on them you’ll notice that they’ll be warnings like “Unused variable ‘xyz’” . . . which is true because you haven’t entered the code that uses that variable yet).