Pros
For most people, a really great place to work. High integrity, passionate and talented employees, generous benefits, energetic environment. Work/life balance is a core value. Some of the smartest traders and technologists I've ever worked with. Their business strategies are largely insulated from market conditions, and they are positioned to profit regardless of the state of the underlying or volatility markets.
Cons
Upward mobility is absolutely capped. You can get paid, but the leadership structure is set in concrete and unless someone leaves/retires, you're staying right where you are. Path to partnership is unknown and unknowable. Traders have a little too much influence on the tactical decisions in technology, resulting in inefficiency and sometimes paralysis. Progress is hard. "Rock stars" are identified and given too much credit/adulation relative to their peers.