Pros
NASA is fantastic for people looking to work on innovative initiatives. It depends on which organization you work in but most managers are flexible and looking to ensure you are happy with what you are doing. The ability to work on side projects with other organizations is pretty high if your management is behind you and you take the initiative to go and look for opportunities. Also, the work life balance is fantastic. Need to skip out early for a dr's appt or take your kid to soccer? No problem. Want to telework on Friday? Sure... at least that works for my organization.
Cons
Lots of red tape to get work done. Often management will chose to take the easier path regardless of whether the harder path was the right one for the long term. Additionally, the low performers are rarely penalized for doing poor work or not contributing enough effort leaving the high performers to pick up the slack. This can be a bit demoralizing as the pay is often not commensurate with your performance.