Adding my two cents here, even though I am ten years removed from this process (so add your grain of salt now, if needed). I was a re-applicant: wait listed at two schools my first time around, but didn't make it in. I did a re-write of my PS, and worked with someone who was an editor to be sure the flow was right and had lots of polish. Most importantly, I wrote a personal statement which was, well, personal. My first statement came across as somewhat cold because I was quoting papers and trying to appeal to the left brain of my readers. When I rewrote this, I was very frank about what my motivation was for doing medicine (not going to share it here, very private about this). I worked with the editor to be sure I didn't cross over into Oprah/Springer land, but I wanted the reader to know that this was not only a logical decision to me, but it was something that affected me to my core.
Whaddya know: the next year, I was accepted to 4 of the 5 schools I applied to, and wait listed at the last one. Same schools I applied to which were pretty indifferent to my application the year before were incredibly responsive with this new PS.
Never underestimate the power of your PS.
Oh, and if you think writing a PS is grueling...wait until your internship year. Seriously.