Pros
You're part of a huge network and if you stay long enough, you'll be able to apply to work in one of their other offices around the world. Some big clients are part of the mix so again, if you're lucky enough to work on these, you'll get to travel for work. Once you've entered the 5 - 7 year working experience stage, you're well compensated.
Cons
Management are woefully lacking in current industry knowledge. PR consumer team have very limited knowledge of social media yet somehow fudge through managing client pages every day. Their strategy and planning team is pretty much non-existent and in terms of trying to compete in with the current focus on content marketing, they're lagging. There were no journalists who were employed to work on one of their largest content projects and instead they outsourced it to a company who did not have the skill set to take this on. What happened to the project? It failed.