- Abstract: The trade-offs between different desirable plan properties -- e.g. PDDL temporal plan preferences -- are often difficult to understand. Recent work proposes to address this by iterative planning with explanations elucidating the dependencies between such plan properties. Users can ask questions of the form ``Why does the plan you suggest not satisfy property $p$?'', which are answered by ``Because then we would have to forego $q$'' where $\neg q$ is entailed by $p$ in plan space. It has been shown that such plan-property dependencies can be computed reasonably efficiently. But is this form of explanation actually useful for users? We contribute a user study evaluating that question. We design use cases from three domains and run a large user study ($N=40$ for each domain, ca. 40 minutes work time per user and domain) on the internet platform Prolific. Comparing users with vs. without access to the explanations, we find that the explanations tend to enable users to identify better trade-offs between the plan properties, indicating an improved understanding of the task.