There is more than enough discussion about the usefulness (or not) of student evaluations of courses. I will refer you to Larry Moran‘s recent discussion where you can find one perspective as well as links to other articles. More recently, there is an interesting piece in University Affairs by Brett Zimmerman of York University.
To some extent, the issue appears to be that anonymous evaluations are not particularly helpful. I don’t know how it is done at most universities, but at Guelph evaluations are now done online on a volunteer basis (so the problem becomes getting them to participate) and only comments that are signed count in T&P reviews. I personally find the comments useful, if in no other way than to provide confidence that some of the new approaches I try to implement are successful.
I don’t think we want to abolish student feedback, and I think this should be part of T&P reviews, especially in disciplines like science where there can be a tendency to consider oneself a researcher first and an educator a distant second. However, unsigned comments, especially when they allow students to make insulting statements without consequences, are not useful and should be updated.