Applied online and received two phone interviews and an onsite interview. First interview was a resume walkthrough and the second was a technical interview. Both went well, and I thought I established a good rapport with both interviewers. The onsite consisted of three panel interviews, one of them technical, and a one-on-one. I felt that I did well in all, and particularly nailed the first two. The only portion I was worried about was the technical, which didn't go as well I though. I sent my thank you's as soon as I got home.
The next day I received a call turning me down. The lead interviewer said that although I was the best candidate they had interviewed so far technically, the most prepared, and the only candidate to follow up, I lacked a certain "sparkle", which he went on to say was unquantifiable, and they were unsure of my CS skills, which they tried to relate a pizza delivery job from high school in my interview. He went on to say that I seemed nervous, despite already having said I was the most prepared, and gave better answers than the others.
This isn't the first bad interview experience I had, and honestly I didn't think my previous worst could be beat, but I found the whole reasoning they tried to give incredibly insulting. I've never been told every reason I should have been hired, then told that although they can't come up with a quantifiable reason to not hire me, they aren't going to anyway. After they played up their company culture, this seemed extremely hypocritical and contrary to it.