Intrepid comes with Totem as the default player but so far I have not had much luck getting it working (playing DVD movies) on Intrepid, but I think it worked on Hardy. Totem comes with gstreamer by default and works with xine as well, but neither seemed to play the main movie, just the copyright bit at the start!
I seem to have had better luck with VLC and MPlayer. I installed these using the add/remove menu.
This guide seems to have a solution that got both VLC and MPlayer working with DVD movies:
Commands used were as follows:
sudo apt-get install libdvdread3
one thing that seemed to get things running ok after running these commands was to reboot the system before trying to play a DVD