Pros
Google offers a great environment where you are constantly challenged and pushed do to more with less. The people are brilliant and you can't beat the social environment and the perks. The culture is very open and transparent at all levels within the organization which is a lesson that other companies should learn from. The transparency truly creates an environment where everyone can share and learn.
Cons
There is a lack of overall organization so if you like a highly structured environment it may not be the best place for you. The company is very data driven which can be a pro or a con depending on your preferences. Google is a very engineering driven company so if you are not comfortable in that type of environment then the company may not be a good fit for you.