My impression is that there are more than you'd expect (there were more than I expected, at least).
I think as med students we tend to be anal about knowing exactly what the expectations of us are so that we can do everything in our power to fulfill those expectations (i.e. exams, evals, etc.). That's why everyone wants to know everyone else's Step I experience, everyone wants to do millions of practice questions, everyone wants to set up their expectations based on NBME assessments.
But the fact is, there's going to be a bunch of questions that aren't specifically covered in any review book. That should be a comfort to you, because if it's not a fact or concept that is accessible to even the hardest studiers (who use review books just like everyone else), it's probably not going to hurt your score. While we don't really know the details on how these questions are scored, I think it's unreasonable to study with the goal of picking those questions up. Trust your instincts. This is where faith in yourself and the system come in. If you studied harder than the next guy, worked harder in your classes (which were probably more comprehensive than review books), and got to a good place with your understanding of concepts, integrations, etc., your gut instinct or ability to rule out answer choices is probably going to be better than other peoples'. So if anything, I'd say the type of questions addressed by this thread may be the ones that people who did well in classes have a better shot at getting, but that's just one possibility.
Personally, I was pretty freaked out by how many were "what the ****" questions and as I said I expected fewer, but I ended up in the 250's.
Bottom line: there's a reason why people say "the best prep you can do for Step I is to do well M1-M2 years", and there's a reason why people say, "during your Step I prep, focus on high yield stuff".
Incoming M1's & M2's: study hard in classes, because it may benefit you on Step I. It's silly to think that since people say Step I matters big time and M1-M2 course grades matter very little for residency, that means it's fine to go through the motions M1-M2 with the intention of just busting your ass for Step I.
People doing final prep for Step I: cover as much as you can as many times as you can, but if you're not focusing on high yield stuff, you're making a mistake. Don't reinvent the wheel, and don't get sidetracked by the fact that there'll surely be questions out of left field, and don't let it get to you on the actual exam.
