IMPORTANT CONCEPT!!!! PLEASE READ!
If you are a first or second year DO student and are pondering competitive specialities, you NEED to take USMLE Step 1. Study hard and take it because many ACGME program directors will have nothing else to compare you to other MD applicants. There will be some PDs who won't care, but its better to be on the safe side because competitive programs and/or programs in highly desirable locals might want the score.
Also, and more importantly in my opinion. Many 1st and 2nd year students, whether MD or DO, have no clue what specialty they want to go into. There's the 1/3, 1/3, 1/3 rule that I heard once. Only a 1/3 of med students will start medical school "knowing" what specialty they are going into and actually go into it. Another 1/3 will decide third year while on clerkships what specialty they want, and the last 1/3 will either decide fourth year or probably end up changing their mind once in a specialty/during internship, and switching. Point being that maybe you want to do EM/Gas now, but after starting rotations maybe you'll decide you want to do Ophtho or Derm...and now what...you've already taken USMLE Step 1 with the thought of going into EM/Gas, and now you might be wishing you studied harder, or took USMLE Step 1 altogether. If you wait to take Step 1 later you'll likely have forgotten quite a bit.
In my example: I was 90% sure that I was going into EM the first two years of medical school and I thought it important to take USMLE Step 1 so that PD's could compare. I thought EM was a fairly competitive specialty at the time and arguably it might be more so now. Little did I know at the time that after a few months on rotations my third year I became interested in radiology. Now its a whole new ball game....."I wish I had done better on Step 1, and maybe I'd get more interviews and feel better about my chances." I thought my Step 1 was fairly good for most ER programs, but when it came time my fourth year to apply for Rads....talk about nervous.
So I always tell first and second year students when I see them, to study hard and take USMLE Step 1, and shoot for as high as you can get. In the end, if you still want to do FP or something, no loss....because it won't be that vital to have a stellar Step 1.......but if you decide you love Orthopedic Surgery....its definitely better to have a Step 1 of 250 going into the application process....it can only help you.