I rotated there last year and one of guys from my medical school is a resident there now. When I rotated there, the residents were openly not happy with the program. The chair, Dr. Hamilton, is openly malignant, or "old school", as puts it. While I was there, he was pretty rough on the residents in clinic, in the OR, & during the morning sessions where they run through the cases that came in the day before. He isn't always like that and not with every resident. There were times he was down right pleasant, but he was malignant a good part of the time. I can't speak for the other sites or other faculty since I spent almost all of my time around him. I hear they have a few new faculty, so it might be different. From what the residents said, the other sites are much more friendly.
I spoke with the guy from my school and he said that is "just how it is" and that "you get used to it." I haven't spoke to him in a while, but he said he and several other residents don't really like it there, but it isn't as bad as people make it out to be. Furthermore, he said Dr. Hamilton is not exactly "up-to-date" on most of his medical knowledge and that he felt that overall, surgical training was lacking at UMKC. I'm note sure in what aspects though.
I don't know how it was during this interview session, but when I interviewed last year, he gave a "fire & brimstone" speech about how the program is rough and if you can't handle it, then you shouldn't rank them. I commend the guy for being open and honest, but it also sounded liek he was trying to justify why he has a bad reputation and why some of the residents may not be happy there. In my opinion, if you have to give excuses about your program on interview day, there is something wrong.
Overall, I don't know if the program is as bad as some people make it out to be, but there is definitely room for improvement. I didn't even rank them last year and am happy at the place I landed.
Hope this helps.