I can't imagine squeezing Step 1 studying in between rotations. I've put in three weeks so far, with one more to go, and from what I hear there is no way you'd ever be able to grab the time during/after a rotation to do this kind of studying. Besides, although Step 1 has clinical vignettes, it's still testing basic science - anatomy, pathophys, pharm etc. and your exposure to that stuff in rotations will be real hit-or-miss.
I have heard that taking Step *2* shortly after doing all the basic rotations is a good idea because of your recent clinical experience, but I've never heard anyone say that clinical experience would help you do better on Step 1.