We were in that first California batch for our old company Inkling Markets. I remember going through our interview and being asked very few questions about our actual idea, and instead Paul asking a bunch of questions about a political blog I was writing at the time. Being consultants at the time working for big companies we walked out thinking what the hell was that and questioning if we even wanted to make this leap if we were offered. But that night at 9pm as we were aimlessly wandering around Cambridge waiting for a call back (or not) we decided we'd do it if they called. "We want to invest in you. You have 5 minutes to decide if you want to come. If we don't hear back from you by then, we'll assume you're not interested." We called back, flew home, quit our consulting jobs and two months later drove out from Chicago to live in a rented house in Cupertino.
We did YC again in 2011 and it was kind of a shit show, but I'll never forget my time out there Jan - Apr in 2006. Probably still one of the most productive, eye opening experiences I've ever had in my entire life.