I've now happily used KTorrent for quite a while, and one day, I wondered about the sense of the File Preview function given in the filelist's context menu. For media files, it works as it seems to be intended for, but why isn't there the same for images or just text files?
Of course, it's not too hard to just open konqui and browse into the folder to look at the album cover, but why should there be a preview task in KTorrent itself if it's not suitable for that a task? Consider people's laziness (and mine, too)...
And since OGG files are simply opened with the standard KDE app, why shouldn't all the other completely leeched files be treated the same, or, even greater, with an additional "Open with..." dialog as in Konqueror's file context menu?

We've added preview functionality for media files since they can easily be previewed even though they are not 100% downloaded. Imagine what would happen when you try to open a binary file which is partially downloaded

BUT, you're right. We could add 'open' or 'open with' context menu entry for completed files. I think I've tried to do that a long time ago but something stopped me, can't remember what...