The majority of M4s have not matched yet. Wait another month unless you only want to hear from all the future urologists and ophthalmologists. I applied to general surgery, which is not the most competitive specialty, so others who applied for those residencies like ortho, plastics, derm, etc. might have a different answer.
P=MD is only for the pre-clinical years. I prefer it this way because it really does take a lot of pressure off. I go to a 5 point school (H/HP/P/LP/F), so I still felt that drive to better myself to get a higher actual grade than just a P. There were definitely some people who took full advantage of P=MD. I definitely liked the fact that not getting a perfect score was not devastating, as many pre-meds believe. There is no way to possibly learn everything in medical school and you WILL get questions wrong. As far as Step 1, I don't think a P=MD mentality will hurt you. Most of Step studying is not based on what you learned during the first two years, but rather on recalling information, cross-referencing between subjects and being able to recognize clues and patterns to answer questions. Most people take about a month of prep and study time before taking the exam, which is so far beyond what you do for a regular exam that they aren't truly comparable. Of course, if you do well in pre-clinical years you will set yourself up to do better on the Step.
Once you get to the clinical years, as far as I know, every school uses a 5 point system. This is because these courses are taken by all students and the majority take the shelf exam at the end. If it was P/F, residencies would have no clue how you actually did in the field you are interested in.
Having gone through the application and interview process, I can tell you that I did not get asked a single question about my pre-clinic grades. I think I had one question about my clinical grades - got an Honors in peds and the interviewer was like "Oh, so it looks like you really did well on pediatrics. Why aren't you going into that?"
Otherwise it seemed that no one was interested in those grades.
Edit: Asked an ortho friend, and he said that his mentality has been P=FM.