Pros
You learn USAID programs and proposal development better than anyone else can teach you in the industry. Great travel opportunities across all levels and plenty of opportunities to gain new skills from proposal management to program management. If you're pro-active and demonstrate business savvy, you can go far here.
Cons
They only work with USAID as a donor so you become a one-trick pony with regards to international donor experience. The company doesn't do talent retention so recognize quickly if you're one of the golden children who has a senior level Director willing to take you under their wing. If not, get the experience you need and go elsewhere for higher pay and better title. Some people are able to identify the opportunities they want and take advantage of them and other times your supervisor or manager will micro-manage the opportunities you are able to take on. Again, recognize which category you fall into and plan accordingly. If you're an Associate or Manager who's not getting the opportunities you need or want within two years, leave.