How do you go about evaluating the accuracy of the themes and action items? Do you create a test set with obvious themes and actions and check the results for example?
You can check specific examples in our white paper: http://www.getthematic.com/net-promoter-score-verbatims/ (Don't need to download it, the bulk of the results is published on the page.)
In practice, some customers have read samples of responses and expect certain themes. Others have manually tagged them in the past. They compare their results with their fundings and can see straight away if our results are accurate and reliable.