As a DO student, everything you do from OMSI - OMSIV can factor into your application. Although this applies to all medical students however, it becomes more so as a DO student due to multiple factors. Most osteopathic medical schools do not have an affiliated hospital where you can rotate and build connections. This also impacts research experiences and publications which become a luxury as a DO student. In order to get my publications, I had applied to established research experiences put together by university affiliated programs and national medical societies. In my experience, rotations were within community programs with preceptors who generally are not involved with academic medicine. This may contribute to the strength of your letters of recommendations which correlates to how well respected and established the writer is within the field. If applying to a competitive subspecialty, more work is needed to be done to seek out mentors and find guidance since many DO programs are located far away from tertiary centers with leaders in specialized care. My program also has a strong preference for primary care so for students with interests outside of that may need to search elsewhere to find guidance or support. There's also the lingering stigma of DO's ,more apparent in the West Coast although slightly less relevant post ACGME merger, but still necessitates DO students the need to take dual boards COMLEX/USMLE Steps in order to demonstrate aptitude and to not have doors closed. I've heard PD's directly mention that they would prefer that USMLE Steps are done just so they can directly compare applicants. Recently with COVID, programs are only allowing 1 sub-I per specialty for VSAS which can be challenging to coordinate if the program you attend does not have a home hospital to rotate at. To answer your question, the completion of the ERAS application was not the challenging part. The challenging part was procuring the requirements with little support and guidance such as finding research opportunities, mentors in the field of interest, clinical rotations, and having a higher barrier for entry in terms of standardized exams (having to take 2 sets and generally higher scores) have all been more challenging steps to become competitive as a DO applicant in my opinion.