Pros
Flexible, relaxed, friendly environment. Paid internships, which can more readily turn into full-time employment as compared to other agencies.
Cons
You have to seek out your own professional development. They are a little uncoordinated and different offices don't talk to each other all that well sometimes. HR is a bit reluctant/stingy when negotiating initial salary, but the agency provides bonuses with product releases and good, fair raises based on experience and work. Really not great about recognizing and developing leadership from below.