I used to be a teacher at a school where we implemented some PBL learning in our classes.
PBL works fine if the student is mature enough of a learner to do it right, and by mature, I don't mean old, but used to being independent. There are plenty of people who finish a 4 year college going to lecture after lecture and never really being expected to ask questions or think beyond the powerpoint slide and what you memorize off the slide. If this is what you are used to and what you like, then you will probably hate PBL.
If you are the type of person who encounters a question or problem and then goes on Google and tries to find the answer, starts asking questions of people around you, etc. then you might like PBL. PBL requires that the person involved be inquisitive and knowledge seeking.
I'm not putting down people who aren't PBL oriented, I'm not always that inquisitive myself, so I probably wouldn't love a PBL school either.
The difference at, say USC, is that you work in groups with 1st through 4th years to figure out problems. I suppose they feel this is like real life where if you encounter a problem or unknown situation in the dental field, after school is over, you have to solve the problem yourself or work with other dentists and specialists to figure out the issue.
PBL failed horribly in my high school by the way...wrong place to try it.
oh, PBL probably wouldn't be too hot for some of the people on SDN. You know who I mean. The people who post 5 questions a day on some of the most common questions "Do schools require shadowing hours? or which schools have supplementals?" that there are answers to everywhere on the net and everywhere on SDN if you did a simple keyword search, but they are too lazy (or oblivious) to search, so they just post new threads hoping for fast responses.