Pros
People at APCO are generally really smart and hardworking; you'll have the chance to work with colleagues of all levels who have already done and will go on to do greats things in their careers. I worked in the D.C. office for three years and made great friends I'm still in touch with. Since the office and company as a whole are in a majorly transitional period, there are opportunities to help shape the culture and evolve your role according to what you want to do (but it's not necessarily easy to - see below). If they get senior management in order over the next few years (assuming the CEO will retire soon), I think the company could turn around but it will be a long and painful process.
Cons
APCO is a very frustrating place - it's similar to other agencies in terms of low pay and long hours but APCO is independent and family run and there is zero transparency about what's going on, which has been especially damaging during this period of change. In 2013-14 there were many layoffs, lots of restructuring, rumors of office closures, loss/shrinkage of major accounts, etc. and we were all left guessing (and panicking) about all of this. Management has acknowledged that people are frustrated by this but nothing was ever really done while I was there to change it, and people just continued to leave the company constantly. In terms of structure, APCO likes to hire people without defined roles and responsibilities, and you'll quickly learn that you're expected to flounder and figure it out on your own, often without an engaged/helpful manager. APCO disguises this as an "entrepreneurial spirit" where you can pave your own way but in reality, it's a big unstructured mess that's especially hard for young people to deal with (which is why turnover is out of control). The reviews and raises situation is equally as frustrating, with people working regular 60 hour work weeks and not seeing fair compensation (reviews are a joke and everyone's basically given the same raise - although they're supposedly changing the system in 2015). And meanwhile there are people who have been there forever sliding along and not pulling their weight but because of the "family" mentality, they won't be let go.