I applied to this program during the last application cycle so I'm not sure if my experience/information accurately reflects the current state of the program. I applied due to interest in one of the professor's research, the fact that they have a center dedicated to working with families and children with autism (my primary interest), focus on licensure (I believe this is pretty new for them; one of their newest faculty members was pioneering this movement) and a desire to apply to a school geographically out of my comfort zone.
During the interview day I found out that my research interest was no longer my POI's primary research interest. I also realized that I wanted to attend a university with more faculty. However, the faculty and students were extremely friendly and professional throughout the interview day. I had a really enjoyable experience. I ended up being accepted into the program and they offered probably the best funding offer I received throughout the cycle (a 4 year fellowship package). I ended up declining for the reasons stated above: small faculty and only a mild match of research interests. In the end, it was not enough to convince me to move across the country. However, for someone who may be more local, these reasons may not have been a deterrent.
What reasons do you have for thinking that the program is not sustainable?