Pros
A very healthy agency environment with incredibly smart people. Juniors get great visibility simply by the virtue that there aren't a ton of them, and there are tons of opportunities for mentorship and to learn from leadership in the organization. They are extremely organized, very kind from top to bottom, and the working arrangements are super flexible.
Cons
R/GA is such a fast moving company that it can be very hard to understand what's going on at any given time. And, for example, when layoffs come it can be hard to understand why. There's a narrative of great performance and a ton of new business wins and then they announce another round without any real indication of what's driving that decision. It happened a few times in my tenure. Though I was never cut in those layoffs, it sends a chill down everyone's spine with a 15 minute all hands is dropped on the calendar that lingers for months as people try to figure out what happened through the rumor mill.