Rating: 

Chapter 1-3 & 5 really helped me to understand the Flex environment and how to work with it. They probably should have been in that order.

I got bogged down in Chapter 4, which is a great reference, but not something to dwell on when trying to learn.

Chapters 7-10 were great, but after getting bogged down earlier, I wasn't much in the mood to dwell on these. Other than that though, these chapters provided a bit of a knowledge base to work off of.

Chapter 11 seemed a bit out of place, but covers how Flash (yes I know we are talking Flex) and hence Flex are designed to work with media very easily. This could have been next to Chapter 13 for effects and transitions.

Chapter 12 is probably the most useful for understanding how to create an application overall in Flex.

Chapter 14-17 covered dealing with data and communication of data back and forth, which I didn't spend much time at all on.

Chapter 18-22 covered the basics of working with applications and dealing with them. Where Chapter 22 seemed to be the most useful.

I pretty much after getting bogged down in Chapter 4, read Chapter 5, skimmed the rest and jumped straight to the last chapter and it's example. I was able to get this working flawlessly.

Overall, this is a great book for learning Flex, however my one complaint is that it is geared towards working directly with FlexBuilder product from Adbobe, which I didn't bother using at all.
No complaints about the book other than that though and well worth your time and money if your going to be working in this environment and there is enough in this book to allow you to extend and expand upon it well beyond what is just presented.