Well moedog, I totally understand your situation. I have been a medtech for the past 8 years and also decided to go the doc route. I have a 3.7 gpa, but my mcat had much to be desired. Let's just say that I took it enough times to have to ask written permission to take it again. Before I took the Princeton I scored a 20. I took the Princeton as well and began with an 18 on the first diag. I know it's a cliche, but I don't take standardized tests well, especially not the mcat. During the course of the princeton i continued to improve everso slightly. Long story short... I went from an 18 on the diag to a 24 on the real thing. Now I know this isn't a blazing improvement, but it is 6 points--good for me. I think the princeton claims that the avg is a 10 point improvement. Just stick with princeton it will pay off.
As for the MD, this is the pre-DO forum. However, I did apply to many of the MD programs with no response due to the mcat score. I am sure that I will take a lot of heat for this statement, but all of the MD programs I am aware of put most of their weight for admissions on the MCAT score, then a little on the gpa and other application points. I say this after much research.
Last year, I applied only to DO programs after talking to a lot of people. I applied with a 3.7 gpa, 24mcat, 8 years of healthcare experience and numerous other application points (basically the same as what I applied to MD programs with). I received alot of interview offers from the DO programs and have been accepted as well as waitlisted to some other schools-- a total 180!! Not only do DO's practice a comprehensive approach to medicine, but it seems that the admission committees use a comprehensive approach in the admissions process as well and tend to see the overall applicant and NOT just test scores--which we all know do not make good docs.
From my experience, there is very little practical difference between DO and MD in today's healtcare practices. 8-10 years ago, there was a noticeable difference in the way that the two practiced. However, with the way the healthcare pendulum, insurance and patient care is swinging, the prevention and wellness approach is a main practice all the way around. You're an RN, you've probably seen it as well.
The big thing that i like about DO is the fact that you have another "tool" at your disposal to aid in your medical practice--osteopathic manipulation.
Good luck with the whole thing. It's a crazy ride, but it's worth it. Hope this helps!