It allows to copy DVDs without menus using dvdauthor, which, as the name suggests, is a tool that helps you create menus, buttons and chapters. K9Copy supports various video and audio codecs, including Xvid, x264, WMV 7 and 8, RealVideo, MP3, AC3 or AAC. It can be set to use either mencoder or ffmpeg for MPEG-4 encoding, allows 2-pass encoding (which is slower but performs an improved, constant quality encoding), and it also allows you to select the size and number of output video files.
It has no fewer than 4 preview modes which can be set in the configuration dialogue: the internal previewer, mplayer, Xine and Phonon.
One of the nice things about K9Copy is that it also provides the option to extract only the audio, which can prove very useful for a concert/videos DVD for example.
The configuration dialogue allows to change the default settings for MPEG-4 encoding, add devices, select the DVD size, enable/disable the use of dvdauthor and customise the buttons' colours, default audio tracks and subtitles, edit settings for video/audio codecs, select the preview mode, and change the paths for the tools which are used by it.
I think K9Copy is the most fit DVD transcoding and backup utility for KDE users. It has subtitle support, an easy to use interface, a preview mode and also dvdauthor inclusion.