Pros
CLS is really good at keeping their clients happy. They produce good work and have staff from many different walks of life who have a good perspective on communications and DC policy areas.
And the kitchen has a margarita machine.
Cons
CLS is not good at keeping their employees happy. People are overwhelmed, overworked, and frustrated with the constant turnover -- more than half the staff has turned over in the past year. Junior staff are expected to complete mundane tasks with little to no time to do them because they are always being asked to fill in on work that is well above their level; senior staff maintain a very clique-y nature that means you're either one of the cool kids or you get pushed out. It is a culture dominated by white men -- even though the majority of staff are female, the top two levels of management are entirely white men, so the lack of diversity is very apparent. There's very little transparency with lower-level staff and people often know that they are being whispered about behind each others' backs.
And they never actually use the margarita machine.