I've got Xcode on my Mac and am going through a couple of the development books. This is a dumb question, but do I need to go ahead and pay for the developer's license while getting up to speed with things? Or, can I just go through the exercises just using Xcode that I already have, then pay the $99 when I'm really ready. Are there other things in the SDK that I would benefit from now? Is the main benefit of doing it now so that I can place my apps on my own device for testing? Thanks.