ffmpeg is a free, open source project - fantastic options, but not a Apple'ish, convenient app... from my p.o.v., not easy to install/to handle...
there are many other tools, converting dvd into something, just to mention DVDxDV (mainly for usage of DVD content in iMovie) or Handbrake (to make DVDcontent smaller, into mp4), or iSquint (to convert DVD into iPod'ish format).
to my knowledge, ffmpegX is just a shareware GUI for ffmpeg, to avoid the huzzle of installing and usage of the original "app"