Succinctly: LORs, if you had rotated there or not, LORs, board scores (to get your foot in the door for interviews if competitive), LORs, grades, LORs, extracurricular activities. Did I mention LORs?
I know for EM board scores will get you through the door at the big name places, and then after that its anybody's guess. I've seen people with awesome board scores get a few interviews and a person with really crappy board scores get a lot. Its a crapshoot.
All you can really do is apply to as many places as feasible for you and roll the dice.
Q, DO