The overall process took just over 2 months. It began with an email from a recruiter with a few questions about my education and work experience. After replying, we set up a date for a 30 minute phone call. The recruiter called, exactly to the minute, and ran through my CV - current role, why I want to leave, previous related experience - and asked questions to determine my knowledge of adwords and my interest in Google. She finished with some competency based questions - example of time you were innovative, etc, and then told me I was through to the next round. She provided a lot of helpful information and good interview advice as well as feedback from the phone interview. She explained the next round would consist of a marketing pitch (you're given a one page information on a client e.g., ABC toothpaste manufacturer and you have to prepare an adwords based marketing pitch based on one of a choice of scenarios) and we set up a date for this.
This time it was a manager on the team who called and we went through the marketing pitch followed by some more competency based questions and a huge focus on why google, and specific examples to each competency/question. About a week later I was informed that I was through to the onsite interviews. This took place a week later and consisted of three 45 minute interviews testing a range of competencies, knowledge of the position & adwords and passion for google. A week later I received another email saying I was successful and that the final stage was to prepare a candidate pack to be sent to hiring committees at the US headquarters.
This is where you get a chance to highlight all your googliness and achievements etc. A week later I was informed that my pack was approved by the first hiring committee and I would hopefully receive an offer if the final hiring committee approves the pack. I received a phone call from the recruiter on the scheduled date with great news and she gave me the main details of the offer. This was followed immediately by an email detailing the offer and benefits package.
The recruiter was absolutely amazing. She called exactly when she said she would, replied emails promptly with lots of information, even replying late at night and at weekends.
The interviews were also really interesting and each googler had different questions and even different interviewing techniques.
Apologies for the long essay, I just wanted to give as much info as possible because I know how useful the info on glassdoor was to me.