Pros
The Alliance still (as far as I know) employs some very competent and hardworking mid to senior-level policy wonks. Much can be learned from working with these individuals. Problems lie with senior management and junior level new hires looking to ruthlessly climb the career ladder. Little recognition is given to work that does not directly relate to homelessness programs or policies (i.e. the communications and research department).
Cons
I worked at the National Alliance to End Homelessness for approximately 2 years. During the latter part of my employment there, the CEO hired new management (specifically a new CFO). This particular CFO had no respect for my job position and after 2 months of working at the organization, had fabricated enough lies to fire me. She was clearly trying to cut the budget, but the way she went about it was beyond unprofessional.
My immediate supervisor, who was also new to the organization, did nothing to stand up for my work or my reputation. It began to feel like I was working in a middle school environment - with half of the staff (the newer half mainly) talking behind my and other people's backs etc. and sabotaging the careers of their coworkers. This kind of environment led to less productivity and under the CEO and CFO who allowed (if not encouraged) undermining and otherwise "catty" behavior, the morale of the entire office suffered.
This organization has done some outstanding work in the past to help increase federal funding for housing for homeless people. Unfortunately, half the employees are now scared to suffer the same fate as I have, and the other half are scared to speak up for fear that they will lose favor with the CEO/CFO. It's become a tyranny of sorts, with these two women ruling the small nonprofit in a disorderly and emotional way that promotes backstabbing and vicious career climbing among their (mainly) female staff. The quality of your work does not matter here. If someone does not like you for whatever reason, you will not know that reason. Instead, you'll be targeted and eventually "let go."