I am going to assume you are talking about Integrated Math. We are using an Integrated math series but it may not be the one you are talking about. First let me say that I have taught 29 years and am very set it my ways. So you may take the following as you wish.
We have been using the series for about 4 years. Our scores don't seem to have changed much on the tests. This year the first group is trying AP Calc and struggling not because they aren't bright but because the texts do not do enough drill and practice and move on before the subject is understood. The students are usually shown the concepts a year later and have a great deal of trouble remembering.
I have supplemented the texts will more practice each year and looked thru old texts for similar problems. I do not use the projects or the writing and reading assignments. Did I mention I am an old teacher set in my ways.
I like the text because it has allowed me to explore topics in math that I have not done before except in college. It is extremely interesting if you are a math teacher but I am not so sure about if your a student.
Over the years I have noticed an erosion of students ability to tackle difficult problems and seem to expect me to be even more of the sage on the stage. This has been caused by students being exposed to topics and have not mastered.
I recommend you look at the text and decide exactly what content you think is important first then decide how you plan to supplement the text. I have always done this but usually it takes a few years to get a complete feel for the text. I have instituted gateway tests in the classroom to make sure students can do certain basic operations before they can get any credit.