Student surveys could certainly contribute to the evaluation of teachers, but I doubt its a viable replacement for academic tests. We must also note that they are being compared to current test-based methods. They claim to get "good agreement" but without a real publication its hard to tell what that means. Does it mean that in most cases the students are honest? (i.e. that the disagreement is caused by dishonesty) Does it mean that in most cases students appreciate teachers that make them learn? (i.e. that the disagreement is caused by students who like their teachers even though the students themselves are not learning) Or is the disagreement inherent in the fact that one measure is better than the other at gauging teacher performance?