In terms of design, this tool is rather simple. It is a single-window application that doesn't have many features or options. Thus, everything is done by selecting settings from a few drop-down menus. You can add one or more files to the user interface and decide what formats you want to convert them to. All the files added to the list will be converted to the same format. In other words, you can't choose different formats for different files on the conversion queue. This is not a big deal since most of the time, users convert files to the same format.
In my testing, I didn't encounter any problems when converting files between the supported formats. Although the application only supports a few formats, they are the most popular and widely-used ones.