Pros
This is a great work environment, relatively relaxed and everyone is very down to Earth. I would describe it as a place to retire. You can get onto an interesting project and won't be overworked, but you can also find a dull project. If you are looking to get down and dirty and grind however this is not the place for you. If you are looking for a job that pays well relative to industry standards, is somewhat interesting and you have other interests and hobbies this would be a good spot as WLB is great. Additionally all of the offices in Mclean have their own rooms! No more public cubicles, although some floors do, you will have your own room, door and window. Cafeteria on first floor and free brewed coffee (not instant) with unique flavors, as well as 1/2 off 2 starbucks stores inside the office. Office has a gym that is about 40 a month, and nobody really uses it. Relatively great benefits but no 401k matching for a year. Super inclusive and diverse.
Cons
Not so stable as of recent Reductions in Force due to DOGE. About 10% of the company laid off. Also being an FFRDC, don't create a product. Less experience you will gain here than a year at another company, but they do pay you more which is a plus. No 401k match first year.