They require you spend many hours at home doing a homework assignment as a test that you know what you are doing. This seems absurd - I can show you my portfolio of large-scale projects instead of doing free consultant work for one of their labs / internal projects - yes, they were real projects they were dabbling with. The interview itself wasn't bad, although it was about 4.5 hours long. The people were very nice and all, but also a bit hung up on process and red tape. If you are in the ad arena, beware there is an ongoing culture clash between the Google Kool-aid drinkers and the recently acquired DoubleClick ad network folks.

The interview process starts with a initial screen call with recruiter (very nice and professional recruiter introduces what's the next and prep advices. Good time to ask any questions you have), 45 mins long one-to-one design interview with a Staff Interaction Designer to present past case studies and behavior questions(advice: Googlers are trained to help candidates to succeed and they are all really supportive. Be yourself, don't be nervous, and be PREPARED!), Woohoo, panel interview with 4 interviewers from different team, starting with 45 mins long case study presentation in the morning, and comes with a 1:1 design challenge interview, 60 mins long. After that, there will be a 45 mins long collaboration 1:1 interview with designer (normally cross functional), another 45 mins long behavior 1:1 interview with designer( you will be asked questions related to your presentation), lastly, 45 mins long design skill interview (questions still about presentation like how you validate design decision, trade offs, design process etc. ).