Heh, waiting for the post-interview phone call was a real nail-biter, we basically spent the entire evening waiting for the phone to ring. But it didn't. It didn't even occur to us that they might call our land line back home until we got the email the next morning. Remotely checking the answering machine was fun too, hadn't used that feature in ages and the code didn't work (turns out you can't send DTMF tones when…
Our email came in the early hours of the morning. I'd encourage you not to respond to it, at least for a few days. I felt compelled at the time to send a few paragraphs the next morning responding to some of the criticisms. Retrospectively it probably wasn't that all that useful to anyone.
It must be an exhausting 3 days for the YC team. I don't think there are enough hours in the day for them to call all the unsuccessful interviewees. Especially when some of them (like us) will want to take more of their time responding to feedback.
The quantity and quality of the questions and feedback you get in the short 10 minute interview alone is brilliant. Even though we didn't get funded it's had a massive impact on the way I think about things. I'd fly out from the UK to do it again even if there wasn't any chance of funding.