Well, from my experience, most schools' AP courses do not teach at a college level. Of course, if you can get a 4 or 5 on the AP, I guess you have mastered the material well enough to skip out on it.
Regardless, I still maintain that taking all of the intro courses is important for 3 main reasons 1) MCAT prep 2) Better preparation for upper-level sciences and 3) GPA. Not to mention the fact, that if you're coming in as a freshman taking a bunch of upper-level science courses, you are going to have difficulty getting used to the workload of college. Taking these intro classes can help ease you into the college environment and give you a sense of the style of teaching, the tests, etc, without being bombarded with upper-level material that is being taught by professors who are under the impression that the students are familiar with the basic concepts already.