Great compensation package, but not good for technical career advancement.
Pros
Great benefits - there are no other local companies that can give you as much compensations with these benefits. You get an "forgivable" loan towards your first house which reduces in principal with every year of service, 25% each year. You get a month of paternity leave which you can use all at once or spread it over the year (e.g. take every Friday off). Flexible hours, work from home, but limited.
Cons
A lot of politics, the teams are very bulky - managers are just looking for "head counts". Too many meetings. Most people will tell you that consultants do most of the work, but there are a few great employees that always put in twice as much work than others. Fannie Mae doesn't believe in firing people - you can do no work for years, but as long as you don't break any rules (porn) then its next to impossible to get fired. This is good for lazy people, but bad for most people looking for advancement in career -- especially since most management believe that head count is better than quality or productive people.