I worked at Zynga for a year + some months. It's actually a good place to work. You learn a ton about social / viral games and monetization, make really good contacts, get paid at or above market salary, eat really good food, and get all the other startup perks. And, you're still doing game development so it's not like your skills don't transfer.

I don't regret working there at all. I just wish the stock hadn't of tanked and the game I was working on hadn't of been a failure =P