Pros
FMG works hard to foster a collegial environment. Management really cares about employees, with flexible hours and great benefits. If you log more than 40 hours in a week, that goes into your vacation, and most managers don't care about what hours you work as long as you get the job done. The work is engaging, and the quick growth means that new opportunities keep coming up if you are ready for them. Salary growth is very rapid if you do good work. The company is very open and transparent, even going so far as to report full results, by working group, from an annual organizational health survey.
Cons
Since it's a small company, hours can be a bit uneven, but management will usually reply to this by increasing staffing. Your mileage can vary somewhat depending on which team you are on, though it's usually possible to change teams with a bit of time.