Pros
Two meals were catered every day, and special care was taken to accommodate anyone's dietary restrictions. I worked in a room full of very experienced game developers from all walks of the industry, including a few legends from my childhood. For the most part, everyone was friendly, helpful, and invested in helping you succeed. Even when the whole team is stuck in the office because your update keeps failing QA at midnight, they come to you to see how they can help, rather than complaining. Zynga offers unlimited/untracked PTO for vacations and sick leave. Their official vacation policy was "You should probably take some." In an industry notorious for working developers to death, Zynga producers were known for pulling people aside and telling them to go away for a week or two for a vacation. And if a producer asks you to stay late to finish something, they'll sometimes offer you a day or two off in exchange. The whole office basically shuts down from before christmas through the new year.
Cons
Not a lot of original IP or creativity, in some aspects of their games. Also, the product managers are making game design decisions based solely on market statistics.