Pros
I work with some of the smartest people in the world. Everyone is 100% dedicated at GS. Additionally, the level of communication is outstanding with everyone knowing what's going on at any one time. We tend to have a lot of meetings which can be viewed as negative (analysis paralysis some might say), but I find it very helpful. Everyone gets involved in the approval process this way, and everyone's voice is heard. The flattened hierarchy at GS avoids all the beauracracy and people can get down to work without worrying about the "proper" chain of command. And lastly, the technical systems that have been built by in-house GS personnel are some of the most advanced and useful pieces of software in the industry.
Cons
Nothing really important that would warrant a comment.