You'll find two kinds of "patient feedback documents" in retail establishments; comment cards and questionnaires. These both provide some of the same information, but a questionnaire has several advantages.

Questionnaires seek explicit information which can be analyzed and trended over time. This allows the business owner to know with a degree of certainty the extent to which business changes have impacted patient satisfaction. Comment cards only provide broad opinions, which often are very valid, but which cannot be used to trend changes in patient opinion. The best of all worlds is a patient satisfaction questionnaire with a "comment" question.

Comment cards are not a complete waste of money, but their value pales in comparison with the information obtainable using a quantitative patient satisfaction survey.