Pros
Smart people. No jerks, they get weeded out very quickly. Commitment to work-life balance, at least in my experience — there are late nights and weekends like any agency, but people try not to make them the norm. Efforts to increase diversity/inclusivity and awareness of unconscious bias. Interesting work for good clients. Career advancement for junior/mid-career staff is good. And unlike a lot of places with unlimited time off, BSD actually encourages you to use it!
Cons
Starting salaries are decent, but negotiate as much pay as you can when you start because even if you get promoted your raises won't be all that much. Benefits are only OK. Not always perfect about living up to progressive ideals b/c it isn't unionized like some of its competitors and isn't committed to salary transparency (they don't post salaries on job descriptions, and people with the exact same title on the exact same team can make very different salaries as a result). Some managers are amazing and some are terrible, and unfortunately there's no accountability for the terrible ones. Career advancement seems to stall out once you become senior.