At the end of a registration, users are given the option of telling us about their experience. There is no requirement to do this. For July, 2015, we received over 1% responses, which is a high rate for this sort of thing. Among those, all responses were "excellent", except for four "good" ratings.
Sometimes we get great information on how to improve, and we always write back if we can answer a question. Ratings are shared with admins.