I have finally finished the iPhone chapter for the book. I've also taken an additional editing pass and finally gotten rid of all the parens at the end of ObjC method names. That was the single most pointed out flaw in the book (not sure if that is good or bad :). And finally I added a full section on CATiledLayer. I will post a blog entry about that shortly that has some of what I learned.
So, the book is getting very close to being done. If you are going to be at WWDC I'd love to meet face to face.