I took Step 1 yesterday, so here are some of my impressions...
First and foremost, I'll say that Kaplan qBank was the best money I spent in preparation for the exam! Being able to set up actual board-style questions in the test format was excellent preparation, and I found at least the tenor (if not the content) of the questions to reflect the actual test pretty well. That said, Kaplan seems to like certain types of questions which were not well represented in the actual test. For example, detail oriented cell bio (e.g. HLA subtypes, specific chromosomal loci) were not nearly as well represented on my USMLE as they were in qBank. Also, behavioral science and biostatistics were significantly MORE prevalent in the exam than on qBank. Folks, those questions are absolute moneymakers; a little time devoted to understanding biostats and evidence based medicine WILL pay off!
As for the rest, I'd say my experience generally reflects that of others who have posted. Anatomy, histo, and embryology are not heavily emphasized (with the possible exception of neuroanatomy). Biochem is present, but don't drive yourself crazy reviewing it in excessive detail; detailed questions MAY show up, but they are the decided minority, and not worth the time investment. Path, physiology, pharm and micro make up the bulk of the questions. I'd say that just about everything in those subjects is fair game, and the more comfortable you are with the material, the easier things will go.
I am certainly happy to have taken it this early, and I feel pretty good about my performance. If I have one regret, it is that an extra two weeks or so would have allowed me a more deliberate approach to the big subjects. I felt like there were a number of questions that I had covered, but went through them so quickly that the material hadn't really stuck, and I was forced to guess at something I should have known.
I'd be happy to answer any questions you guys might have, but there will be a little delay, since my vacation starts today (woo hoo!). Hope this helps; good luck to everyone!