Pros
Strong commitment to living by the organisational values - people first, keep it simple, make it real. These aren't just taglines or "words on a wall", but are truly demonstrated by every member of the team. People care and give their all to make the collective team a success. Unlike a lot of larger consultancies, people actually want to hear your opinion here. There is not a lot of politics and hierarchy, unlike what you see in other traditional corporate employers. The culture is great and supportive and the work is meaningful.
Cons
There is a lot of autonomy and self-directed work. This isn't a "con" but anyone coming from a traditional corporate setting may find it overwhelming that no one is making your schedule for you and there isn't a policy and procedure for every little thing. The most successful people here are not afraid to take initiative. You are supported, but not micromanaged.