Structured Problem Report Formats have been key to improving the assessment of usability methods. Once extended to record analysts' rationales, they not only reveal analyst behaviour but also change it. We report on two versions of an Extended Structured Report Format for usability problems, briefly noting their impact on analyst behaviour, but more extensively presenting insights into decision making during usability inspection, thus validating and refining a model of evaluation performance. Author Keywords Usability Evaluation, Usability Inspection ACM Classification Keywords ACM: H.5.2 ? User Interfaces