Willget800,
You must realize by now that this whole process is subjective. You got an interview invite at Chicago GSB and at LBS - two very difficult programs. You got your interview at Cornell, a school that has seen (if rumours are true) massive increases in volume this year. You've made it through some of the most demanding parts of this entire process, and although I know that the ding stings, you, of all the people on this site, should know just how random the whole thing is.
This is just one application - you've got 3 more sitting out there and you've had interviews with ALL OF THEM. That says something about your candidacy I think - in of itself, it's an impressive feat. I realize that getting within 10 yards of the finish line doesnt mean anything unless you get to the finish line but things are still looking very good for you here - I honestly think you have a strong chance at your remaining schools.
It's a tough pill to swallow, but find consolation in the fact that a lot of other prestigious top schools have already indicated your candidacy is worth seriously considering - and that Duke's decision to ding you must therefore be purely based on some random element you could not have controlled.
I'm truly sorry to hear Duke didn't play out for you, but don't give up, please don't give up.