Pros
Very safe and professional work environment. Sexism doesn't live here, you're evaluated on what you do, not what you look like. It's the ideal - knowlege, science and technology for the betterment of humanity. NASA really is the coolest part of government and it's great to be part of a team that believes in furthering knowledge and technology for the public good - rather than just for profit.
Kontras
The biggest asset is also the biggest liability. You really have to be an idealist to work here. The pay and perks are far below what you'd get at an equivalent position in a private company. You'll be participating in pot-lucks instead of dining on chef-designed cusine every day. Retirement? You're looking at social security and whatever you can tuck away in a 401K, which won't be much unless you happened to buy a home in the area 20 years ago. The red tape has been increasing lately, thanks to a hostile and anti-science congress, so the paperwork burden, for even necessary, things is increasing, but still better than most other government agencies.