Pros
Best people to work with - somehow they manage to create environment where as we are in trenches together, we're also becoming so close we are in each other's weddings, baby showers, etc. There are massive growth opportunities if you work hard and good systems in place for your colleagues to reward you when you're performing well. They have frequent reviews and an open feedback mindset so it's typical to receive a lot of real-time feedback and generally know how you're performing without having to pry for it. It's very laid back culture-wise, even though there are obviously titles that are higher than others, there's not a competitive, "I'm better than you" attitude, everyone really does want to help each other grow.
Cons
Work-life balance is hard, just as at any agency. Introverts or quieter people may tend to watch louder, extroverts climb faster. This comes with the job though, if you're comfortable voicing opinions and ideas, you're more visible and more likely to be given new opportunities.