Pros
There really aren't any. Others comment on good compensation; I'd say it's average at best and most certainly NOT worth the level and stress and expectation that you will work 24/7. Oh wait, the food. They did it big for clients and were generous with their employees as far as parties and what not.
Cons
Unfriendly, overworked, miserable people. It's one thing to have to work hard, it's another to work hard in an environment that is confrontational and not collaborative. Management receives and reads EVERY email that comes in and out of the agency. Picks and chooses when to get involved. Will expect that you will respond to clients at all hours of the day. And will call you out if you do not do so according to their ever-changing expectations.