Vantaggi
Good work/life balance, compensation, and benefits in current age. Up to 22-23 days leave after 3 years. Very diverse staff. Provides a number of specialty benefits/incentives, for mass transportation, adoption, home purchase, and partners. At least within IT there is opportunity for exposure to high-end systems, processes, and best-practices in any of a number of areas typical of large companies and financials in particular. There are quite a large number of skilled and motivated people, but it's still possible to find a niche where you can be influential if you desire. Company can serve as either a very good transition into financials or large enterprise shops (if you're not afraid to push for experience in different areas), or as a decent long-term stand if you're not very ambitious and are willing to put up with the beauracracy and many idiosyncracies. Based in Washington DC area where economy is generally more stable and there are generally a number of other companies interested in skills you could acquire here.
Svantaggi
Moderately bureacratic and fairly siloed; what could be a decent performance system has been warped by "unofficial" policy of grading teams on a curve (only downward), and results in very limited number of highest rankings available even for the very high performers; very few opportunities for advancement (at least on IT side) and some favortism in assignments (leading to high rankings) results in a lot of turnover of high-achievers they really should try to retain. GSE home ownership mission results in frequent bashing by republican politicos as well as revolving-door exec jobs for democratic ones; a significant number of employees historically stay due to the secure job and good compensation and just are in the way; bloated middle-management (an inverted diamond, not a pyramid). Recent government conservatorship likely to result in either the end of the company or at least nationalizing it (making it even more government-like).