Pros
The biggest pro is the culture - I feel supported by all of my colleagues, and you get the sense that everyone wants to see their coworkers succeed and grow. Management is also very transparent about where we are and where we're headed. There are also ample opportunities for advancement - since this is a small company, there is always room for you to grow and take on more responsibilities. The benefits package is excellent! Health, dental, etc. plus each employee gets a philanthropy budget and a personal development budget to use as they like.
Cons
Work schedules can vary - some weeks you are looking for things to do, and other weeks you are working overtime on a project. As far as I can tell, this is pretty typical of any job in the market research industry.