You should go and attend. I just had mine this past Tuesday. We formed small groups, three applicants and one alumni, and basically talked about anything Cornell. Most, and I really mean most, of the alumni are friendly and understand what you're going through, albeit there are always a few that tick a nerve. That said, my interviewer told me that he has to write a report after the interview and that if there were any good points to mention, he would. He also said that he wouldn't write anything negative about us, but I can't guarantee if other interviewers will do the same. I absentmindedly didn't bother to reply to the three emails they sent me and had to go through some extra trouble to get a spot, but the organizer did warn me that if I did choose not to go that she would have to notify the admissions center about my lack of interest. Unless you're super super super super busy or if Cornell is just a safety school, I would whole-heartedly recommend you go; it can only boost your chances, and besides, I'm sure you're a pleasant and genial person.