I personlly do NOT believe CPM is rigorous enough for college bound students. While it is very accessible for students with lower math aptitudes, it is very watered down and does not teach proper mathematical terms. This causes difficulty when they get to a traditional type setting, as they're constantly behind the vocabulary curve.
We also use CPM for Algebra 1, Geometry, and Algebra 2. For Precalc & Calc I chose the Hughes-Hallett books, because they are very conceptual and do provide opportunities for the students to really think about things and explain themselves.
In my experience, however, students don't really think about things and how they're applied. They want to get it DONE, not understand it. They want an A, not an education. It's incredibly frustrating. Most of my AP Calc students can't graph a line in the form y = mx + b. It makes me want to tear my hair out!