Pros
The people and talent really make this business what it is. Some of the best, brightest, and kindest in the industry.
Cons
All of the negatives of being a part of a "big" agency with little (or none) the benefits.
The work. Tight timeframes, limited scope for agility, lack of long-term strategy, and inability to influence trajectory or organisational change. Being a specialist service as part of a larger conglomerate often ends up simply becoming a vendor, inheriting all of the risk with none of the reward.