I received my copy of Macromedia MX: Building Rich Internet Applications today, and I am very impressed. Robert and Simon do an excellent job of making the MX suite of products really accessible to beginning AND advanced developers, and I think everyone can find something of value in the book. I think they achieved a good balance between theory and hands-on, practical exercises in order to help you to not only grasp the concepts, but also learn how to apply those concepts to real application development.
I think it is important to point out that this book is not intended to replace other books that address each of the products/technologies in depth. Instead, I see that this book does two very important things: First of all, it helps readers find a really solid starting place with all these technologies in order to know what does what and how. And secondly, this book complements other related books in that it is the only book (that I know of) that shows you how to integrate all these products to produce rich internet applications.
As always, Robert and Simon have translated their knowledge, expertise, and experience into a format that is easy and enjoyable to read. I have worked together with both Simon and Robert, and it is a real treat to see the fruits of their collaboration. Macromedia MX: Building Rich Internet Applications is a real winner.