The interview at Google was a deep but interesting day-long process. After the regular screening phone interviews with HR, I got invited to their offices for almost a full day, where I got to meet about 9 people in one day, each for one-to-one interviews. The key problem was that these people were not communicating with each other, so I got to say a lot of things over and over again, but each one was very laid-back and simple. The final interview was with the Managing Director of that specific division of Google and was the most inspiring, mostly a simple discussion with an extremely interesting person.
The overall process was very tiring, but it lead me to meet with very interesting people, so I got away with something at the end of that process, if not the job itself.