The comprehensive is nowhere like the real thing, and neither were the individual shelf exams. You want to find out what the real step 1 is like? Then take the NBME self assessment #5 and #6 (the new ones). In terms of the types of questions asked and the format of the questions (as well as the difficulty level) they were 100% identical to my step 1, seriously, I was shocked. NBME self assessments #1-4 were identical to every shelf exam I've ever taken, and they were pretty easy.
I'll say it again, if you want to find out what the Step 1 is REALLY like, take NBME self assessments #5 & #6, and really study how the questions are asked and get the logic down. Now, on what subject matter the questions will focus on in during your real step 1, you can only find that out the day of the actual test!!! Don't listen to the people who try to break things down into percents, like: "15% of the step 1 is Neuro, and 40% of the step is Path". My step had more ethics questions than pharm and neuro combined, so it's different for everyone. It's a long test, so other than knowing your material (which is a given), there is a big endurance factor in taking the Step 1 and endurance is just as important as knowing the information. 336 questions spaced out over 7 sections of 48 questions, so try to eat a good breakfast and a decent lunch to give your brain energy (DO NOT just drink Red Bulls! You'll be all twitchy from the caffeine and you have to wait till the end of your section before you can run to the bathroom). But trust me, study hard, do lots of questions, and above everything else, BE CONFIDENT, and you''ll nail it!
"Courage is all about doing what we're afraid to do- there can be no courage without fear"