I wouldnt risk not taking it, and then having programs judge you based on a score they might know very little about. I am for the notion of giving the PD's every possible tool to compare you with other applicants. That includes the USMLE. Once you are applying, it is really too late to decide you want to take it, because the program you want to go to requires it. And some programs dont explicitly require it, but I will always believe that for GS, you need it. Too much DO bias still exists in this area, and what better way to present yourself than with good USMLE scores: "beat them at their own game".