We investigate the relations between user perceptions of work task complexity, specificity, and usefulness of retrieved results. 23 academic researchers submitted detailed descriptions of 65 real-life work tasks in the physics domain, and assessed documents retrieved from an integrated collection consisting of full text research articles in PDF, abstracts, and bibliographic records [6]. Bibliographic records were found to be more precise than full text PDFs, regardless of task complexity and specificity. PDFs were found to be more useful. Overall, higher task complexity led to many highly useful results, and high task specificity led to many useful documents.