Pros
Great co workers, no idiots, an intelligent bunch. Interesting and challenging work. Good social events.
Cons
Flat chaotic structure. Finding useful information is nearly impossible. A lot of it is in peoples heads. What is commited to store is often out of date or wrong. They still think Excel and file shares are a cool way to manage projects. No KPIs for projects. Lots of technical debt. Consultants often just hack out the same solutions multiple times. Maybe in Python, C++, Java or whatever was on their laptop at the time. They have a narcistic "Broadway is Best" attitude. So end up writing their own colaboration tools and group messaging frameworks. This is in preference to concentrating on their core business. They only pay 50% of your benefits. The other 50% comes out of your salary. So check this detail with them before you join.