Animated scatterplot visualizations promise to be useful tools for analyzing trends in time-oriented data. We evaluated such a visualization for the analysis of time-oriented medical data. We found 10 medical professionals to test the software which visualizes clinical diabetes patient cohorts. To analyze the usability of the software, the methods "Thinking Aloud" and structured interviews were used. Results show that animated scatterplots do support medical professionals in their daily work, in contrast to more negative results of scientific research in the past.