Pluspunten
Depending on your role, 8+/hr workdays are common, but it's comforting to know you're supporting a good cause. Most employees (and volunteers) are willing to go above and beyond for the company mission. If you are highly skilled and motivated, it's a great place to leave your mark. Management is very open to changes (especially if it means greater efficiency and better use of donor dollars), but you must be prepared to fully support and carry out your ideas. Talk is cheap, and tangible actions are highly valued. If you're not particularly skilled, but highly motivated, it's a great place to sharpen your skills. Management is willing to invest in your learning curve, but expect to be tasked with the same requirements as everyone else.
Minpunten
The organization is going through some growing pains, so there are many on-going changes. To survive, you'll need to keep an open mind. With new changes, understand that mistakes do happen ("Never attribute to malice that which is adequately explained by stupidity") and that everyone is trying their best to improve the overall organization. The pay is acceptable, but obviously doesn't compare with a for-profit company. (If you're expecting a high salary, why would you work at a non-profit?) If you're unmotivated by the organization's mission, you're going to have a bad time.