R/GA has gotten too large for its own good. It makes you feel like a tiny, expendable cog in a huge system. This has also made it hard for people to reach out to higher management to discuss anything related to your career or other matters. It definitely got clunky. For instance, you could get stuck on a boring account for years and it would be very hard to get yourself heard and moved to a different account to keep learning and growing. That can take its toll on your portfolio, as well.
Office space is quite nondescript and depressing, and there is very little sense of integration and community, despite the open layout. Mostly people silently starting and their computer screens.
It is also incredibly difficult to get promoted, or even get a raise. I have worked there for 5 years without a single actual raise worth speaking of, even when I got a change in title. And I know many people around me who are in the same position—many of which are resigning or looking forward to do so. This phenomenon has more to do with office politics than the work of their employees. I have done my share of 60+ hour weeks and weekends and felt very little acknowledgment or appreciation—and forget about time or monetary compensation. They definitely need to work harder to make their employees feel valued and have their efforts and dedication acknowledged.
On a similar note, there is very little mentorship, coaching or guidance. Many times, I felt like I was being left to my own devices or out of the loop altogether, with very little knowledge of what's going on internally or with the client.
Oh, and people with big egos abound and can make your experience there really, really miserable.