Pros
They help you find a job, go over your resume, reformat it, make it the way the employer looks for. Keep buzz words to a minimum, but help build summary..
They negotiated the offer, interview prep, and treat you like a person. Like that they help you find an alternative job not just your job title. When took a placement they contact me monthly to check in and sent a gift basket of coffee.
Cons
Cannot think of any, maybe more outings for teams