I think you missed this one from Aptly, posted just last week: http://www.nancyhua.com/2014/10/08/successful-y-combinator-s...

edit: Also, this site has a list of interview experiences of people who got accepted and rejected: http://ycuniverse.com/yc-applying-interviewees

In some ways reading about those who got rejected is a little more informative.