Pros
Flexible schedule, as long as you work 80 hours every two weeks, they really don't care how you get them in. Excellent benefits for the most part. Top notch health plan. Casual work environment, jeans, sneakers, etc. And for the most part everyone has their own office. No cubicles. Three weeks vacation to start with, four weeks after 2 years.
Cons
There's no real career advancement path unless you really carve one out for yourself. Almost all work is federal gov't, so when there's a shut down or a sequester, work dries up. Also, it's all about billable hours, so if you get stuck at home because of a blizzard, you're expected to find a way to make up those 8 billable hours. Same thing if you're traveling for work. That time in the air, you better be working on something billable. They have a good profit sharing match they put into your 401k, but only once a year instead of spread out over every paycheck. So if you leave anytime during the year before that payout, you won't get a penny of that payout. You get a lot of vacation time, but only six paid holidays.