Pros
May not be a "pro" for all people, but I like the small company atmosphere. It means you are able to actually get to know the people you work with.
Office has a laid-back feel; you do not have someone constantly over your shoulder watching you work. Casual Fridays. Able to wear sandals. Office potlucks.
Employees are encouraged to attend training courses and seminars to better their skills and further their careers.
Open door policy with owners - you have the opportunity to talk with owners almost every day if you want (and if you work in the main office).
Exciting, ever-changing industry to be part of.
Good benefits, including a number of different medical options to choose from, good amount of paid vacation even when you first start, paid mileage, overtime, etc.
Cons
A small company means that there are probably limited opportunities for advancement (unless new positions are created).
Sometimes you feel a bit "thrown to the wolves" to fend for yourself so you do not always know what to do, even in training. Would be better if there was more opportunity for hands-on training where you could shadow another person.
With multiple locations, you may not work in the same office as your boss, so it can sometimes be difficult to connect and get feedback/responses/meetings.
Sometimes there seems to be a struggle between the way things have been done in the past and new ideas.
Not enough paid holidays