All this discussion really shows (yet again) is that you need to have done the research for yourself and you have to know for certain that the school you apply to is going to be able to offer you what you want from it. In the end, only you know your goals and if you do the research you'll know best if the school you're looking at can fulfill them.
The thing about Duke is that they should room to grow still.
As for the class makeup, I got from chemical engineering degree from one of the top rated programs in the nation and there were some "mediocre" folks there as well. That didn't affect my education at all, nor did it affect the fact that I had access to faculty that were the leading experts in the world in what they studied. Obviously, it's not the same situation in B-school (nor am I claiming Duke's faculty are the best in the world), but you can't make your decision on the class makeup. I'm sure there are some mediocre students everywhere you go. I've run into a few arrogant jerks at some top schools, but that wouldn't cause me to stereotype the entire class and not apply there because of it. And frankly, if you're going to be the worst performer in the best program, you might be better off being the best performer in a top-15 school.
terp's list is a list specific to why he chose not to apply, my list might look very much the same for a school that I've chosen not to apply to, in the end it's a decision you need to make.
Finally, the ethics scandal really means nothing, especially after the latest GMAT scandal, which just goes to prove that Duke was forced to deal with something that unfortunately happens everyday at every school (graduate, professional, or UG).