Pros
Very friendly people, very laid back. Everyone keeps a close watch on the door and only talented, non-jerk ambitious kind people come on board. There are very few locked doors. If you have the time and ambition to make something better, you can, and you own it, and no one makes unreasonable demands of you.
Cons
The downside to having lots of opportunity and potential is that you might often feel guilty about not doing more. So if that applies to you, be wary. The product decisions are traditionally all made by committee. This often leads to underwhelming products even though everyone is talented, because this culture of being kind leads to few coherent decisions and a lot of input from a lot of people ends up washing out more pointed ideas. Also the size is ridiculous and this is due to reasons inherent to a venture capital sort of company, they just need to have a lot of employees. The more employees the stronger the company seems and the more growth they can realize. This has made the company change from a giant family to more of a "normal" segmented business where no one knows anyone else but, as we are all employed here, we are part of the "size" of the company, and it's hard to complain about.