A few schools seemed to really pay attention to this (Brown, others?), on at least a couple of the files that I saw across the interviewer's desk the AOA status was bolded up front. Not sure if this reflects how much they actually care about it. Don't recall being directly asked about it during interviews. I was senior AOA and no distinction seemed to be made between junior vs senior that I could see.

If you look at stats on this site it would seem that the majority of matched applicants are AOA. In reality according to the charting outcomes 2011 data only 27% of matched applicants were AOA for ortho. This number is still high compared to most fields, but it is not as high as derm, plastics, rad onc, and ENT. New outcomes data will be available this year and I expect the AOA% will go up, but still be in the minority. I doubt junior vs senior AOA makes much difference at most schools. AOA vs. not AOA is certainly a big deal, but its not a deal breaker for matching somewhere. It would be very interesting to see a % AOA breakdown by program becuase I'm sure many top programs select strongly for AOA. Too bad this data doesn't exist.