Pros
Yes, the agency has blue chip clients - you'll get to touch some prestige accounts. It has all the "big agency" bells & whistles -- fancy office digs, free Starbucks. There are some talented individuals there.
Kontras
Highly political. Atrocious on-boarding. Not respectful of those who come from outside big agency or outside Edelman -- skills notwithstanding, it's more about the "process" there. Rewards come to those who follow the rules (if you can figure out what they are) and make the right friends in high places, not necessarily those who are most skilled. During my tenure, VERY volatile leadership environment - massive turnover, lack of quality hands-on management for senior level talent. Nearly impossible to find quality mentoring -- everyone is too busy and agency doesn't value it, so it's not a priority. Reputation as a "best place to work" is, to me, laughable. Lots of lip service to the culture - but not a healthy work environment. Little to no socialization with colleagues -- competitive and highly political. Tendency to rest on laurels and not push the envelope with truly creative work. Effort to become more "full service" has them poaching talent from ad agencies - but "creatives" used to ad agency model don't work well with PR account teams...lack of respect between the two disciplines creates tension.