Pros
You get to work on problems that have incredible scale, reach, and impact. You make things used every day by billions of people; or create data-driven algorithms on a scale not done anywhere else. The company has gotten bigger, but the culture is still idealistic and bottom-up. In the end, the thing that makes Google unique is the idealism of its leadership. The press is sometimes cynical about the "don't be evil" mantra, but it's something the leadership is serious about. It comes out in the incredible (but quiet) care devoted to protecting the privacy of customer data; or in the care about employees (like healthy food, thoughtful benefits, etc). The idealism is also reflected in the projects that get funded: not so many projects that chase the gimmick-of-the-day; more projects that lay out a vision of a better world. An excellent place to work over the long run.
Cons
The bottom-up culture is not for everybody. It can sometimes feel chaotic, as if managers can't decide what they want. That's because the culture of the company is "try things and see what works." It is a good company if you thrive on uncertainty and autonomy; it is less good if you are looking for clear, consistent directions.
