I didn't like Northwestern for a lot of reasons:
1) The interview. I think that it went fine for me, but I hated the entire process. The interviewers asked tons of questions that had no relation to medicine, only to try to make the applicants look stupid. I was asked questions like--"if you could be an animal, what kind would you be?," and other equally weird questions. Others that I know had the same experience. To me, there is something fundamentally wrong with interviewing in this way. Out of my 15 interviews, this was by far the worst experience.
2) The curriculum. It was mostly PBL based, and while PBL is the new "hot" method of teaching, I think it's hard to learn from a PBL-based curriculum. The students were constantly complaining about it when I was there.
3) The cost. Their financial aid department, from what students told me, is weak. Very weak. Compare that to Pritzker, which gives tons of merit and need based aid. I don't think I would pay 150K more to go to Northwestern than to my state school.
4) The facilities. They have a nice, new hospital, but in general their hospital system is regarded as nothing special. Compare that to a similarly-ranked school like Pitt, which has one of the top ranked hospital systems in the country.
5) The gut feeling. Everything about the place just didn't feel right for me, on a personal level. I have many friends that had an entirely different experience. But you have to go with your gut in this process, and my gut tells me that anywhere would be better than Northwestern.
The area of Chicago, however, was gorgeous. It was so nice that I really wish I had liked Northwestern.