I got waitlisted the first time I applied. I think part of it was the lateness of my app. I submitted the primary fairly early, but because of trouble procuring a DO letter, my secondary wasn't in until mid Feb. However, I did get an interview immediately after the secondary arrived abd I interviewed in early march. My MCAT is decent, but my GPA, both cumulative and science, were nothing to write home about.
The second time around I was definitely much earlier- had my secondary in before my primary was even verified in mid to late Aug. I interviewed in early Dece. However, on top of that, I had another year of volunteering in an underserved peds/prenatal clinic under my belt, in addition to a really great DO LOR, and enrollemtn in a biology master's program to show some more grades for myself.
Basically, I think once you get an interview here, they are VERY interested in taking you. However, they obviously can't take everyone. So at first, if you do well at the interview and the adcom likes your file, you'll likely get in. The later it gets, the competition for seats will of course increase.