Pros
The variety of the projects that I work on--in terms of both subject matter and clients--keeps me engaged as an employee. My colleagues are incredibly smart and talented, and the collegial environment facilitates opportunities to learn from them as much as possible. If there's a research method or analytical approach that I'm unfamiliar with, I'm usually able to find a colleague who would gladly explain it to me and show me the ropes to the point where I feel comfortable executing it. Professional development is not shirked here, and upper-management encourages actively looking for opportunities to develop (through both internal and external resources). The work-life balance is also great; I hardly work more than 40 hours a week, and when I do, those excess hours get banked toward PTO.
Cons
As a company experiencing growing pains, fewer and fewer faces and names are recognizable to me. I imagine it has become more difficult to maintain that collegial and collaborative environment, especially for newcomers who may not have already established a network of helpful colleagues.