Pros
Work life balance can be quite good depending on your team. In many teams, employees are able to take flexible half days on Friday, although this lifestyle benefit may or may not be extended to future years. Pay and benefits feel very reasonable at the lead contributor and advisor and become very cushy at the director level and up. Relationships with coworkers are more collegial than competitive.
Cons
Fannie Mae is subject to high levels of oversight from regulators, so lots of time is spent fulfilling regulatory requests that often feel pointless. The data science technology infrastructure is unstable; on any given day, I don't know whether the development environment I'm required use will be operational or not, which really limits productivity. Advancement opportunities into management are minimal People interested in management tend to leave the company and then come back after they have outside management experience.