Pros
You will work with some of the smartest people in your field, and always have opportunity to learn new things. For the US it has a quite good corporate culture with much individual freedom. Compared to the Nordic countries in Europe, it's about par for the course compared to startups and smaller companies. Compensation is good, but is also geared towards keeping you at the office more (food benefits and various services etc). Privacy concerns are taken seriously; access to personal data is, contrary to popular belief, very hard to get. You will be able to play with aggregated, anonymized data.
Cons
You're expected to work hard and much. The "20% time for your own projects" is a myth; more like 120% time. If you're outside the US, count on there being late night and early morning Hangout meetings with US/India several times during the weekdays. If you're working in engineering but not as a software engineer, you will have a hard time getting good performance reviews, as all teams will value their own higher than outsiders. Compared to other companies in more forward-thinking countries, Google is about par for the course compared to individual freedom, but you still have have the US-styled meddling micro-managing bosses. There is great inertia in making things happen at foreign offices; things that were implemented in the US took 1-3 years to happen in Europe. If there was a tax deductable benefit that was available in your country but not in the US, it could take even longer to get it set up. The really good benefits never make it outside Mountain View. The workplace in most offices is really crappy; the norm is small desks (hope you're not sitting opposite someone with long legs), crappy chairs, people bunched up together. Unless you work in ads, you should be expecting your project could be shut down at any minute. If you work in ads, you'll be under pressure to make more money to the company. Even if you implement a change that increases company revenue by millions of dollars, don't expect that it will affect your bonus or salary more than an extra $10k or so - you've proven your worth, but if they pay you too much, you might leave to pursue other interests.
