Pros
Interesting projects and big name clients. Its a great resume builder and I learned a lot about market research during my time there. Promotions can happen quickly for certain types of people. Culture wise, they try to make it a fun place to work with very flexible work from home policies, and dogs in the office. Also, the health insurance benefits are amazing.
Cons
Greenberg is one of those places where some people do well and others don't. No doubt, everyone is very smart, but it's hierarchical and top down, so there are a lot of "important strategy meetings" among the leadership, but work gets hot-potated down to the most junior person.
Not everyone works as hard as others, and sometimes promotions go to the best talker and presenter, not the hardest worker. Although there are a few women in leadership positions, it's mostly a male-dominated workplace where the women are expected to do a lot of the grunt work. When leadership asks for your opinion or feedback, those who praise leadership while omitting real concerns are better received then those who submit honest feedback. Hence, there's a lot of ranting behind people's backs. It can be extremely frustrating for people who are straightforward, while those better skilled at office politics do very well at Greenberg.
Although surface perks like snacks and catered lunches are in place, work life balance can be difficult to achieve. Expect to work weekends and holidays. The salaries are also on the low end, and annual bonuses don't always happen.