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I believe that this interface should be quite efficient because there really isn't much for the user to do except to select the images he likes and to drag them to his sketchpad and analyze them. The simplicity of the layout should help also. There are also two main modes of the interface - browsing, and analysis. This is easily toggled using the close button and the Analyse button, I believe this interface is fairly efficient.
Safety
I believe that the interface is quite safe to use. There isn't anything difficult to go wrong, because it is simply not allowed by the interface. However, there can be two places where it might be unsafe. Firstly, the user may erroneously drop something into the recycle bin and be unable to get it back. Secondly, the user may accidentally hit the back button of his browser, and lose his chosen items. This can be solved using cookies in the browser.