Incredible mission and volunteers with hearts looking in the right place.
Cons
Zero concern, compassion, or interest in its employees. Leadership is fearful of everything, and takes that fear out on the overworked, underpaid, employees. Senior leadership likes to say things like "you don't understand what its like to ...".
You feel great at the end of the day when you work for a global cause like the Red Cross. There is never a dull day (if you are doing your job right), and compared to many government or private sector institutions, you can make a difference quickly and get projects rolling without the usual red tape (don't get me wrong - there is still some).
Cons
The best and brightest employees tend to obtain high proft (i.e for profit / competitive jobs). My personal experience was that a lot of staff and big hearts, and even awesome ideas, but often lacked the skill, confidence and work ethic to get the job done. I was also slightly concerned about the overly social portion of the office - chatter doesn't always lead to results. You will be living on a smaller salary when working for a non-profit (which is understandable) - so make sure that you love your job and remind yourself of the great cause behind each project.