Pros
Fannie Mae in general has somewhat competitive compensation and benefits packages. There are some departments that seem to function normally, but it is the exception rather than the rule. If you find a bright leader to work under, stick with them, because there aren't many to be found. Support for volunteer activities was a plus.
Cons
Fannie Mae is a company floundering in an overall lack of direction and an unusually high level of ineptitude in most levels of management. There were certainly some smart managers and employees, but too many were not. While many of the problems at Fannie are self-made, some are due to not being able to do much of anything without the guidance and approval of an extremely slow to react regulator, which is a political beast in itself. So in the end you have ineffective management trying to implement the direction from a regulator that can't decide what it wants to do. What you have left is a bunch of managers fighting for some kind of relevancy and trying to survive at the expense of others in the company.