Pros
Depending on what projects you are pulled into, you can work on some pretty interesting stuff with a group of very passionate people. Junior staff tend to organize sports teams and various happy hours outside of work, which is nice. Work often provides a great learning experience for people interested in getting into government work. Junior staff can get their hands on very technical work if they push for it. Generally good work life balance, if you make it clear to managers that you will only work 40-45 hours per week.
Cons
Compensation is far below industry standard unless you are an engineer. There is a very present corporate structure to many things in the office - lots of hierarchy in compensation, promotions, and decision making. Though ICF denies it, promotions are generally based on how much time you have spent with the company (or whether you have a graduate degree) instead of how well you do your job. Annual salary increases are a joke. Decision-making processes generally need to go up the chain of command. Junior staff generally are not allowed to participate in budgeting conversations. Some managers are too consumed in their own work that they forget to foster the growth of junior staff. Merit bonuses are 1/4th of referral bonuses. Why?! Company seems to care more about shareholders than their employees.