Just some added info for the original poster and other applicants to digest at their leisure/own risk:
1. Where I'm Coming From: I am a fourth year at a US News top 5 school, with an anesthesia program consistently identified on this website as one of the top four or five programs (please note, I went to an unheralded undergraduate institution, and understand/agree with criticisms of these rankings--this ranking does, however, verify that NIH funding here is greater than some countries' GNPs...)
2. What I Know: I recently sat down with both the PD and the chairman of anesthesia, and both had the exact same opening line of questions in this exact order--how did you do in third year? how did you do on your boards?--upon which their appraisals of my competiveness at various programs were based, i.e. the PD told me to "pick any city you want" based on these TWO facts...
3. What I Took this to Mean: I think that PDs are salivating at the increasing competitiveness and qualifications of applicants, and are interested in buffing their stats regarding academic acheivement and average board scores. I very much felt that, in their assessment of me, THE most important questions were the two above. There was no question about research activity, volunteer work, etc. In fact, in a second meeting with the chairman regarding doing some research in the department, he had no recollection of me, my face, or the fact that I spent an entire day in the OR with him two weeks previously--my entire existence, really. He did, however, blurt an "oh, yes, of course!" when he re-asked me the above two questions, in particular my Step 1 score...
4. Bottom Line: I agree with the poster that said third year performance, strong LORs, and a good board score (230-240+) will command at least an interview at all the top programs. Research and volunteer activities are nice on paper, arguably can be used for helping to decide between two equal candidates, but will not fetch an interview for an applicant with average grades and boards.