When I interviewed with them for the SRE position I was extremely nervous (I was right out of college, and Google had contacted me rather than me submitting my resume) and the guy on the other end of the phone for my first interview seemed uninterested, had a really bad quality phone (I could hardly hear his questions), and kept asking the same questions over and over in different terms, and I really couldn't figure out what he was looking for as the "right" answer.
The Unix trivia was not nearly as bad, that was easy as I had done a lot of reading on it, however some of the data structures I was asked about I had never learned in school and had just read about on Wikipedia so I didn't really understand them well enough.
The second interviewer was absolutely fantastic, and was genuinely interested in me as a person, had checked out my resume and looked at some of the previous projects I had done (Near Space balloon launches were discussed). I felt much more at ease, but I did seem to have somehow mixed many of the different programming languages I know (C++, C, Python, Java, F#, Scheme) thus my code was less than clean.
Ultimately after 5 different phone interviews I was unfortunately told that I was not a fit, that they would keep my resume on file and that I could try for another position when I had gained some more professional experience.
The Google interview did help me get through many other interviews I had the pleasure of going to. I was less likely to be caught off guard, especially since it was my first MAJOR interview with an extremely large company. I do wish that Google had not been my first interview as maybe then I would have gotten further into the hiring process and maybe just maybe I would have been working at Google.
That is an awful lot of maybes and it is not worth brooding on what could have been. I am extremely happy with my current job, I love what I do and the people I work with at a small new startup. I feel with a small company I can make more of a difference.