Pros
Since being purchased by a large pharmaceutical company, it's a stable and low-risk work environment. People are friendly and sociable, in the short term it's generally an enjoyable place to be. Compensation and benefits are solid, though by tech standards not exceptional (e.g. doesn't match 401k).
Cons
Flatiron has a culture that doesn’t care what gets done or how well it is done, only about who gets credit. When an executive praises an initiative, teams leap into action to claim credit or to “contribute”, which means being invited to meetings for which they add nothing except wasted time. When a client complains about a problem, every team finds reasons that it's not their fault, or better yet invents a reason that it's not a problem at all. (Actually solving the problem for the client is the lowest priority). Meetings are the vast majority of everyone's time, where credit is divided up and where people lobby for the approval of senior management. Even small ideas need to get sign-off from 10-12 people from many different departments, since that lets everyone in the loop claim credit and increases their department's importance.