Pros
Size, you could find friendly and talented colleagues. Good Opportunities. Very generous pay and benefits compared to other firms. Nice People in the beginning. Not very design intensive, if you are mediocre a designer, it could be a great fit. Company social is very nice. Top-down directive leadership.
Cons
It feels very unorganized in the design process. Also, The design has fallen behind the market and it is not competitive with other firm's work in my opinion. The senior leaders say they care about the well-being of their employees, but in a number of situations, I felt unsupported. The company cares about the profit the most and if you are passionate about design should avoid joining Gensler for extra $. But you are welcome to try it. I regret my decision, but I have learned from this experience so that I can share it with anyone who asks. My colleague all said the extra $ was not worth compared to how much work-life balance they had to pay.