I haven't taken the PASS program, but I have sat in on lectures from Dr. Francis (who runs PASS), since he is an alumni of my medical school.
The man is a genius. He has created a program that, in a clever way, has stripped all of the little details out of medical school concepts so that you can learn the basics, and then after he has cemented the basic concepts into your head, he goes back to those details and fills them all in.
I feel that this course is not necessary if you have a strong basic science background, and have done very well with learning the details in M2. However, if you have come out of M2 feeling like you are not confident that you will even pass Step 1, or if you passed exams and are saying "yeah but I had no idea what I was doing", then this type of program probably makes sense.
People fly in from all over the country/world to take the PASS program, so I have noticed.