[ma2rten]

I work at Google, based on personal experience I would say it does a good job of setting a minimum bar in terms intelligence and coding ability. However, it might reject some people unfairly.

A little bit of preparation helps a lot, but beyond a certain point preparation doesn't help anymore. All interview questions require solving a new problem in the interview itself.

Depending on the interviewer and question, the difference between a hire and no-hire recommendation can be quite marginal. There is a huge luck factor involved.