I know Zynga's reputation isn't exactly sterling as of late, but my experience working at their headquarters in SF was wonderful. Everyone I met was incredibly nice, the employee accommodations were top notch, and despite being the young intern I felt like the work I did was important.
The general issue I detected is that (at least in my department) no one was fired up about the game we were in charge of making. Mind you, there wasn't any real negativity present in meetings, but there felt to be a general malaise and confusion about what we were making.
That's not to say that I wasn't surrounded by sharp, talented people. Rather, I felt that our efforts would have been better put to use on a game project with a more clear vision of what would make it fun.
In short: Great environment, nice and talented people, a bit unfocused vision.