Pros: Very smart co-workers, interesting projects, cutting-edge technology, great benefits and perks.

Cons: Career growth/promotions are hard. Workaholic colleagues make work-life balance difficult.

Pros: If you want impact, Google is a good place to start because of the large number of users there. Even if your change just affects less than 1% of queries, that's easily hundreds of millions of users a month. Infrastructure is also great; you get less distracted and get to focus on quality tuning.

Cons: Systems are quite mature, so if you don't have your own ideas, you may have a hard time finding the right change with potential impact.

Pros: A very high percentage of people are very qualified for their jobs. Everyone knows that everyone else can be trusted to get work done, and this creates a great "flow" for projects. This is in contrast to most other places I've been, where there is always someone on each team that isn't carrying their weight. The management is generally light and easy-going (in my experience), and people just do their jobs. There seems to be a genuine effort to improve employee skills. I have no doubt this is simply for the company's sake and not due to love for the employees, but it's nice nonetheless.

Cons: The side-effect of everyone being good (and everyone else knowing it) is that there is a lot of pressure to not disappoint anyone. The side-effect of less management is that feedback is hard to get, and good performance and hard work can go unnoticed and unappreciated. A focus on technical expertise means that there is less focus on soft skills. Many managers are not good enough at managing people, even though they are very good with the technical side of things. Culture encourages one to give up the rest of his/her life for their job. Despite the initial utopian feel and propaganda, it's just a really rich company with a lot of smart people. It still IS a company and has the same stupid politics, competitiveness, and issues you find everywhere else.