As someone actually in PBL I feel I should chime in.
One thing that is clear is there are some people who simply could not do it. They realized it early and transfered to LDP. The thing is, I am by no means a reader. It takes me forever to read anything, and honestly last year, I was just as nervous as you guys because I didn't know what to expect. As of now, I love PBL and am happy with my decision.
As a physician, you're going to have to study a lot on your own. On top of that, in 3rd and 4th year, if your school makes you take the shelfs, you are going to have to read from big convoluted books on your own with minimal direction. PBL prepares you for that by having you essential do that, albeit with better books, in my opinion.
Before I started, I talked to a lot of people, and the most consistent thing about PBL was that (1) the free time is great, and while you study for hours on end (its still med school) you aren't stuck in a lecture hall and you can organize your time, but (2) your MS1 grades take a hit. Pretty much everyone gets a C on the first test, and even later, a minimum amount of people get As. That said, what you learn, you learn well, and obviously the board scores show the results.
In med school, a lot of what you do is self-driven. You have to be motivated. You just have to ask yourself, if I have to, can I read hundreds (700-800) of pages of med school textbooks in a month? If you can motivate yourself to study for 6+hrs a day, you can accomplish that, and that's coming from someone who hated reading before med school and is still one of the slowest at it.
Unlike popular belief, they don't pick out random minutiae and test you on it. They test clinically relevant or board relevant stuff. You have a set of things everyone learns each block, and then based on the cases, you as a group select sets of readings from all of your textbooks. Its a little awkward at first, but you quickly get used to it, and you see the overlap in textbooks pretty easily. Some people read the whole set of readings 3+ times. It would be impossible for me to do that, so I and about half the other people read it once then review/skim it again the week or so before the exam (if I have that much time). You can also use board review books since most blocks have themes that are repeated in each text reading. Favorites include: FA (obviously), Pathoma, Goljan, Kaplan videos, BRS, etc. A lot of people also like Firecracker.
If you are confused about something, or you aren't sure what to focus on, you can look at review books, or just talk to the professors, who are each responsible for writing exam questions for a designated subject. They are helpful, and since its PBL, they are around in their offices a lot.
It was tough initially to adjust, and sometimes its still tough to stay motivated (because I'm a procrastinator), but I really like reading these books, and I love the material. I also know that I'm learning it better than I honestly learned anything before, probably because I'm actually reading the books.
If you absolutely know you can't motivate yourself to do the work when you aren't lectured at, PBL is probably not for you. If you think you can live with reading lots of books, and can learn that way, at least try your luck with an app/interview, you may end up loving it like I do.