Pros
Free goodies, flexible time and WFH, benefits, casual dress code, weekend away, socials. Some of the engineers are very good.
Cons
Trayport is the master of propaganda. They say you will be able to learn interesting technologies and then you learn how to meet deadlines by cutting corners. They say you will work in a relaxed atmosphere and then you face witch hunts and bullying. They say you will work with talented developers and then you discover that most of them left already. They promise internal mobility, but what they really mean is moving desks (Trayport loves to shuffle people). You read some great reviews here and then you discover that they are fakes written by Trayport management. A special thing about Trayport is their obsession with processes, methodologies, Kanban, Agile, Scrum, you name it. Management sees and abuses methodologies as tools to micro-manage engineers. Before deadlines Trayport uses the following "methodology": in the morning you are told what to do, and in the evening you report status to managers. And, because propaganda is important, they say it is Scrum (just with one day sprints).