Pros
Your colleagues are smart, motivated, inventive, and helpful. If you work on the right teams, you can pick up a ton of useful knowledge in a short period of time from world-class experts. The company is attacking plenty of exciting technical problems: machine translation, huge distributed systems, creating smooth AJAX UIs, large-scale machine learning in search & ads, creating a mobile phone OS from the ground up. Again, depends on what team you're on, but there's no excuse to be bored with the technical challenges.
Parts of the company (e.g., Chrome, Android, mobile apps like Latitude) are blazing new ground and still feel like a start-up; in those areas, there are opportunities for entrepreneurial engineers to make a big impact (although this can be a struggle).
Food is excellent.
Cons
Big company syndrome. We have dozens of VPs and hundreds of directors. Some are good; all have their own agenda. Successfully launching something to our users is a matter of convincing the right set of people, not building a great product.
Hiring bar is lower than it used to be. There are lots of great people coming in, but also plenty of mediocre and some bad hires.
Company is much less transparent than it used to be.
