Evaluation is a different issue for artists creating commissioned work than for administrators running a public art program.
In my view, the administrator needs positive public feedback to politically (and financially) support the program. As artists we need feedback that help us become better artists.
It is much easier to imagine an evaluation of a whole program than to measure the value of a single artwork.
As artists we are all somewhat eccentric in our art making process. We combine research and rational thought with personal intuitions and observations in our own unique ways. We invent things that have not existed before.
Members of the public, who have not seen anything exactly like it before may love it or hate it at first sight. They may adapt to love it, or get bored over time. People who say they love the art, may never pay much attention after the first look. Others who are uncomfortable may eventually come around and gain something important.
My experience is that a large percentage of people pay very little attention to public art.
My sense is that general surveys of the public’s reaction to the artwork would tell me very little in terms of how I would go about creating my work. Of course it is essential to avoid negative reactions that would endanger the public art program that feeds us, although this is not always possible.
The feedback that means the most to me and effects the way I see my work, is the occasional thoughtful response, when someone has established a relationship with the work over time and makes the effort to tell me about it.
My work is about creating opportunities for people to interact with each other and their surroundings in public. When hear these reactions, I carry these observations over to the next project. A few in-depth responses mean a lot more to me than tabulated surveys.