I rotated at northwestern and think that overall, it's a strong program. If you rotate, you are basically only competing with 50 people for 9 spots (assuming you get an interview).
Strengths: Very strong sports with great faculty, good hand, Foot/ankle, good lifestyle, very nice hospital, residents get the top notch fellowships, overall, the residents seem like a good group of guys, lots of teaching conferences in the morning (they do have saturday conference though)
Weaknesses: Don't see a ton of trauma, many of the patients are private and even the senior residents end up retracting in some cases, little resident autonomy at Northwestern Memorial (I'm told it's better at Evanston and VA/County), spine and joints rotations could be better though they said they are hiring 2 new joint faculty