Pros
Sure, the perks are fantastic—free soda and food, bring your dog to work, choose your own hours—but the real fabric of what makes this place great is the trust senior management has in all of their employees. You're respected and treated like an adult from day 1, instead of having to spend months or years proving you're worth respecting. Senior management genuinely believes that their employees can go about their day without micromanagement and hand-holding. Because the employees are treated with respect, they in turn respect the company and maintain a good work ethic. Collaboration is also rampant among the employees, even across departments.
Cons
There is a bit of a "rockstar" attitude amongst the developers (not all of them, but a substantial amount). The truly arrogant ones usually don't last long (or don't get hired in the first place) but there are a few cases where the company's encouragement of the rockstar mentality is all that's needed to make someone a primadonna. Also, positive feedback is everywhere (which is great) but constructive feedback on performance is hard to come by unless you actively seek it out.