I have been using this book with my 5 year old twin girls, and have such mixed feelings about it. We are half way through. Some things I love are the structure, it is scripted and somewhat rigid. That means less work for me in terms of figuring out what to cover. I love how it teaches phonics, which is incredibly lacking in the school system near us. I also like the whole brain approach the book takes. As a neuropsychologist, it's nice to see the integration of writing, sounding out, comprehension and memorization, especially since reading is such a whole brain activity. Making the associations between writing (a parietal lobe function), saying the sounds (temporal lobe function), comprehension (frontal lobe/whole brain) is what good, forgetting resistant memory is all about. I like how the book also takes you through question asking about the picture at the end of the story, focusing the kids on what they might see based on what they read, and then getting them to think about what the characters in the picture might be thinking about (theory of mind, good for autism).
Some things I don't like: the structure. Honestly, sometimes the script is agonizingly boring, and I can't stand that you go through some of the words/stories once, and then have to go back through them again a second time. Plus, my girls are freaking out by that time! Although going back through the story a second time and asking questions is excellent for comprehension.
The biggest thing for me is just managing my own expectations, recognizing when my girls (who are partially deaf anyway) have reached their fatigue point, and letting it go to another day (which is SO hard for me, I want to get things done!).
I've also started switching it up with reading repetitive early readers, like "Dick and Jane" books, and the leveled readers from their kindergarten class. This helps with the boredom/frustration and is good for getting sight words into their long-term memory without doing flashcards. I definitely see progress in my twins. I am hopeful they will be reading independently on some level, any level would satisfy me, by the end of kindergarten.
I wish I had known about it when my son was this age, he struggled to read with the method taught at our neighborhood school - which was, "look at the picture and try to figure out what the word is", totally crazy - and he still struggles, though he has made great progress.
Overall, I think this is one good tool in helping your children really learn to read and sound out unfamiliar words