Context-aware applications promise better usability as they make context information which is relevant to the user accessible and can thus improve interaction flow. However, the quality of the presented information, as well as the way they are presented to the user, can be expected to have an impact on whether an improvement can be achieved. In this paper, we present a quantitative assessment on the improvement for a typical productive application in which context information is presented in an adaptive sidebar. Manipulating the context information quality in terms of accuracy and completeness, our experiment shows that both have a significant effect on usability: Whereas information accuracy significantly impacts execution time, completeness affects task result accuracy and mental effort. Overall, the user experience of the context-aware application was judged to be of high pragmatic and medium-to-high hedonic quality.