Pros
Lots of great people, interesting projects
Cons
50-60h weeks with no time off and the occasional week on-call with around the clock alerts WILL result in you burning out. When I joined the recruiter told me about how people are encouraged to take time off between projects, but the reality is when you get ahead on a project they pile up more work for you. It doesn't matter how hard you work to get ahead, they still just pile up more. All this delays your project so at the end of the quarter you barely make your deadline; then the next quarter and the next project comes up. After 16 months I finally gave up and left, having had not a single day off (I was on call for many of the holidays as well). They didn't even pay me for my two weeks of legally mandated vacation I never got to take, the cheap bastards. Few career opportunities for engineers unless you want to become a manager. Worthless equity that's a risky tax liability. If you have any sort of marketable technical skill and drive, then Zynga is probably a waste of your time.