It's definitely a narrow curve. I just got my score back - 780 - and I'm more than happy with it (>99th percentile). Here's my thoughts: It's definitely a detail heavy test. It helps to know all the toxins and how they work.
Many questions are clinical, but the clinical portion is usually pretty stereotypical and easy to figure out - the challenge is selecting the right answer for that organism, which will require knowing random details about its structure or virulence factors. Also, they won't use names for diseases but rather will describe the symptoms observed for a case. For example, they won't tell you the kid has scarlet fever, they'll describe the symptoms and then ask what lancefield group of strep it would be. The microcards vingettes are pretty close to the actual test, minus the question part.
Basic bacteriology is huge. You have to understand how phages and transposons work. Same with virology. I found Lange really useful for this as I have no real micro background to speak of. I spent just as much time studying these chapters of Lange as the chapters on the actual organisms. If I had only used my MicroCards I would have missed a lot of that detail.
I had a lot of parasite q's on my exam and was glad I studied that stuff. I was told that they were low yield but I definitely had a fare share of parasite and fungal q's on there. Fungus is always pretty buzzword heavy. You'll get the dude from Bakersfield with cocci or the cave-diver from Ohio with histo.
I really liked Lange and used it for the course and for my only review source for the shelf. For review I was able to get through it a few times. It's a big boy, but you'd definitely miss some details with MicroCards or First Aid as your only source. That said, without enough time, a more concise source might be better. Lange is kind of a gamble because of it's size, and you have to focus on knowing all the big points before spending time on the little details. But the details are money.
I've heard a lot of good stuff about Lange's questions but I found that they weren't formatted close to the actual exam. They are probably good for reinforcing points from the book, especially if you haven't read it, but if you've studied the book I think they're pretty low yield and too straightforward to give you much of a test taking simulation. I actually didn't use any question banks or do any practice tests before the shelf...but I would wager that something like Kaplan Q bank or maybe UWorld would be useful. There's a style to some of the questions like experimental data type questions that I had not seen before, and it's probably an advantage to have done some good board-style practice questions.