Interviewing with Google was a great experience. I should first say, I was first contacted for a phone interview after submitting my resume internally through someone I know there. This is a great way to get noticed. Anyways, the first phone interview was pretty standard, and I got along well with the recruiter. She was pretty hard to understand on the phone. I was invited to interview on-site in Mountain View during the same conversation! I was surprised, but rolled with it.
They flew me out to Mountain View, and they payed for flight/rental car/hotel/generous amount of food every day. It was awesome. The interviews were not too hard. I wasn't asked any of these "brain teaser" questions you read about all the time, although some of the questions did test your ability to think reactively and quickly. My strong point was expressing my personality, interest in the position, and fit for the culture. If you've made it this far, there's no question you're qualified already. Just be excited about it and be yourself.
After four 30 minute interviews, I left Mountain View and 3 days later was contacted by the recruiter saying the team liked me and wanted to move forward with me. Now, I thought that an offer was coming, but I was wrong. The recruiter asks you to prepare some notes for her on all sorts of questions, such as your accomplishments, hobbies, experiences, and leadership examples. The idea is to get a sense of how "google" you are. Then, the recruiter contacted all my references and put together a packet of everything my references, I, and the inteviewing team said about me. She then submitted this packet to Corporate, which then gave the "approval" to give me an offer 2 weeks later. All said and done, the process took like 1 and a half to two months.
Overall: I think the "hype" surrounding the Google interview process, at least for this position in particular, isn't appropriate. Getting contacted in the first place is half the battle. From there on out, it's all about being cool, having concrete examples of your experience/leadership, and being able to relate and be friendly with the Google people. Just enjoy the ride.