Pros
SG is great about giving you a chance. Definitely recommend it to younger staff that would start as interns - if you're new to the industry and can show you're passionate and ready to learn, you'll do well. Lots of opportunities to jump into new projects, if you can make time for them. You get the time between Xmas and New Years off, so that's kind of a free week of vacation, in addition to a fairly typical vacation policy. Cool clients doing exciting things. Great snacks. Lots of trainings (general and level-specific). Very smart people all around that you can learn a lot from.
Cons
That being said, like most PR agencies, you'll work long hours while you're at the bottom of the totem pole. Part of that comes from team leads that just say yes to whatever the client wants, and other times its because there is just too much to do. Often times senior people question why an assignment would take so long, but it's a tedious task that they haven't done in years and would take much longer to do if they did it themselves. Some clearly have favorites. Last year's unlimited vacation policy was executed very poorly and caused lots of issues. Go through regular periods of low morale. Some people that left to competitive agencies didn't even get a goodbye toast (that used to be standard for anyone leaving).