Full disclosure: 240's USMLE, 660's COMLEX
Every DO should take the USMLE, if not just to understand how HORRIBLE the COMLEX is. There are questions that made me laugh out loud in the testing room. As future physicians and educators, we should strive to better our profession, and one area that needs betterment is our licensing exam.
I also think that the highly competitive DO students are driven away from the ACGME programs because we are told all along that we have no chance in the ACGME for things like NS, ortho, rads, derm, etc. I was constantly told to not even bother with the ACGME for my specialty. I ended up splitting my Sub-I's between DO and ACGME programs and ended up matching in the ACGME.
I'm sure that one reason there are so few DOs in those fields is that, like me, we're told over and over that we have no chance, despite how competitive we might be. It's not like I rocked step 1 that much, but I took my chances and matched ACGME in a very competitive field. I think we should be encouraging the cream of the DO crop to enter the ACGME in competitive fields so we can continue to break down these barriers.