Here's my contribution:
I majored in Biology/Genetics at Duke, took the MCAT in August 2002, and ended up (at the time I was applying) with a 3.69 GPA and a 38T MCAT. So, I think my scores had a big part in getting me -to- the interview. My GPA was around average - I think it may be what's holding me back at other schools (*ahem* WashU! ... excuse me 🙂 ) Their secondary does require you to understand the basics of how they teach at NU, and figure out how that teaching style fits with yours. I never got any comments about my secondary, but apparently something worked.
Some weaknesses to my application were late research (I didn't start until late Junior year, so I only had about three or four months on my AMCAS), and low 'true' medical volunteering (I volunteered at a touchable art gallery for the blind and visually impaired, unfortunately that doesn't have as much clout, IMO, as more clinical volunteering).
I think well-rounded extracurriculars help - I played violin in a few musicals on the side, drew a campus news comic, and did a lot of stuff with my arts-themed selective living group. LORs are probably key, as well. It can't hurt you to develop good relationships with your faculty.
I do think the interview was very important. Even with a 'high' acceptance rate of 50% like other posters have mentioned, I think an applicant must show enthusiasm and the ability to communicate well with others. I felt like my NU interview was the best out of the several I had that week (busy week, that was), and I felt like it was probably what clinched it for me.
I don't know how NU 'responds' to out of state students at a state college, but I honestly think that NU evaluates people as individuals, moreso than numbers. I think if you'll be ok if you're around or above the avg. GPA and are also a well-rounded applicant.
Best of luck with your application!
04DukeBio