Pros
Great culture!! Purpose-driven colleagues. Great location in the middle of Arlington, and a brand everyone respects. With many jobs you might be in a rush to get home from work so you can take off the branded polo shirt before you go to happy hour but not at the USO. It's almost like a badge of honor in the D.C. area. More than a few times service members have offered to buy me a drink or have said "thank you" because of those three letters on my shirt or cap. When you leave work every day, you feel like you helped change someones life for the better. The health benefits are great. So good, in fact, that even my wife who works for a healthcare company doesn't have better coverage. lol. True story. She makes like three times my salary and she's on my PPO. haha.
Cons
Arlington is expensive, and being a 501c3 non-profit the USO isn't breaking the bank with super high salaries and they shouldn't be expected to. That would only decrease their GuideStar ratings. They also have not been very keen on the idea of working remote, so you might have to live out of town and commute in, which is doable here with Metro. Fortunately if you do have to take metro the USO gives you a monthly metro stipend as one of the benefits, so your commute should be free. In my experience the only other "con" I've seen has been the limitation of personal and professional growth.