I don't know if anyone is interested but there was a forum involving the people who wrote those NBME exams and they even admitted that the form one is very accurate to what you will score on test day. It was so popular that they hurried up and made 3 more that even the creator admitted were not that good. This was information dictated to me from someone who used to be a test writer for the NBME and was at this very meeting. Like everything with Step 1 there is no magic crystal ball I really have learned its different for everyone but I personally would take it right before and if you are not ready you could always push the exam back. If you waste the best of the indicators out there which is form one, when you haven't even begun studying yet I think you are not getting an accurate representation of what your score will be on test day...If you want to know what you need help on there are tons of sources out there that can guide you in your studies like Qbank, USMLEworld, and others. Why waste the best one off the bat...but thats just me.