Opportunity to work independently and make as much of a contribution as you'd like. Unlimited scope and range of technologies with which to develop proficiency or even expertise. The work environment is friendly and mostly supportive. There is very little bureaucracy. Management is flat and fairly approachable.
Cons
Very little direction or formal management. Self-managing to a fault. Little opportunity for job change within the firm due to size and lack of structure. Job reviews and salary increases are infrequent, if at all. Management changes seem to be on a whim rather than part of a larger plan.