Pros
The organization has an exceptionally complex and challenging mission, that spans a huge array of opportunities including Signals Intelligence, Information Assurance, Research (more PhD mathematicians than anywhere else in the world), Technology, Logistics, and a huge array of support and enabling functions. Despite the characterization by the media, they continue to operate legally, with supervision by all three branches of government, and I am just as proud to have been part of the team here as I was to be in the 82nd Airborne, the Ranger Regiment, or any other assignment I had in 16 years prior to coming to the NSA. The jobs here and the locations are so diverse that one can literally do a career reinvention, numerous times, and stay under their employ.
Cons
Like any large organization, there are always challenges with lack of agility and layers of management (I use that word conspicuously instead of leadership) that may be excessive. Younger employees earlier in their career may find working there tough in high expense areas as the wage scale is more modest early in one's career.