I was taught math in high school using CPM and those experiences are why I chose teaching as a career. I remember being in college and being able to explain the "why" a concept works while other students were trying to memorize material. CPM built a pathway in my mind that I was able to access because I had a deeper understanding of the ideas and how they fit together. Now I am able to share the program with my students.
I now see the same results with my students. They don't just know the Pythagorean theorem, they know why it works and where it comes from. The discovery and applications of the ideas are things that stay with the students for future math classes. There is a connection that allows students to apply the new ideas over and over. CPM is not only teaching math; it is teaching problem solving skills for all parts of life.