Pros
The people were some of the smartest people I've worked with in my career and all seemed extremely motivated and encourage people to take on responsibility. I felt like I could go to anyone for help and get an answer. They have cutting-edge technologies attracting really fun clients to work with. I was consistently engaged in creating new marketing solutions and campaigns that had never been done before for the biggest apps. There was something exhilarating in consistently working with "the next big" app months before its launch.
Cons
Fewer formalized processes - you have to be comfortable finding answers where there is no manual. The Flip side of working on the newest technologies on flagship apps and pushing the envelope is sometimes things break and you need to manage the situation and come up with a fix quickly. Getting office space was difficult or a quiet moment was difficult but this might be fixed by the new office space. Creature comforts were also a little lacking, but seem to be getting better every year, like free beer.