Pros
The culture is great: you have flexibility, great coworkers, awesome challenges. Expect lots of work, not lots of bureaucracy. Make things that matter, have impact. Some nice perks: afternoon meals, great offsite events, some free food, free beer sometimes, subsidized gym subscription, health care for you and your children (spouses are not included, though), lunch tickets. There is incentive to personal growth, with corporate programs designed to that pursuit.
Cons
Your work always accompany you, which is somewhat stressful. The company is small, which handicaps career opportunities a little. The biggest drawback is compensation. Expect to earn half than you would in a major player (Google, Microsoft, etc). Bonus is limited to 15% of your yearly salary, but you will probably earn 80% of this value at most.