PCSOM2002;
Sounds like you're right on about the limitations of not doing an AOA Internship. As far a sitting for the Specialty Board Examinations: you can write the American Board of Family Practice examination after completing a Family Practice residency offered through the ACGME (AKA: MD program). The American Board of Osteopathic Family Physicians (or something like that...) examination is available for physicians completing residency in an AOA family practice program.
Also, any DO who trained in an ACGME (MD) program who did an AOA internship before starting residency could sit for both specialty examinations (AMA and AOA). Now with the changes that have come about with the "Unity Program", the AOA is allowing DO's who didn't do an internship to sit for the AOA specialty examinations as well.
What about the limitations of doing an AOA internship? If you plan to do an allopathic residency, there may be poblems with funding for all years of the ACGME program if you do an AOA Internship year before "MD" reidency. These are real problems facing a few of my classmates who did an Internship and wanted to do an ACGME OB/Gyn residency. This is something to consider that you may not get a clear answer on by your school... (I think there's real pressure from the AOA on schools to keep students in the AOA fold.)
Maybe I'm paranoid, but seems like the AOA has had a policy that isn't in the best interest of DO grads. The AOA internship is a good idea in theory, but it isn't for everyone and although there are some excellent AOA programs out there, there are not enough slots at these good programs for all DO grads. I didn't do an internship because I wanted to go to the best program I could. That argument doesn't bode well with the AOA when I petitioned to get my first year of ACGME residency counted towards the AOA internship requirement.
If the AOA wants to "Unify" DO's, they need to amend policies that divide DO's at the beginning of their training.