Pros
Great coworkers and friendly environment. Competitive benefits package, with lots of vacation and sick days. Covers about 50% of your commute costs (if you use the metro). Encourages continuing training/education, but not equally across departments. Work from home is an option. Flexible hours and great location.
Cons
The compensation is less than satisfactory, as this is a non-profit. You're expected to produce high quality product for less pay. There is also a disconnect between the higher management and its staff. Exhibits lack of understanding on issues important to the employees. Very low budget in areas where its most needed. Not all departments receive equal opportunity for employee training and continuing education. Some send their staff out to conferences regularly, whereas other departments are unable to make such an investment.