I have canceled one interview, and it felt a little awkward, but it also felt a little empowering with a shift in the balance of power that only comes with an acceptance. So, not exactly "fun," but it felt fine, particularly because it was one of my instate publics that ran me in circles over documentation regarding my residency status, delaying my app for 6 weeks.
Similarly, I have another 5 schools I am waiting to hear from post interview. I care about 2 of them, but the other 3 are totally irrelevant now, and I am considering withdrawing my app before they get a chance to reject me...and some of the ones that have me on a pre interview hold may get the same treatment from me.