In Ubuntu 8.04 it’s surprisingly hard to change default applications to something of your liking.
Sure you can right-click a mp3 file and set it to be open with the player of your choice, but that’s not enough.
What if you want dvd’s to be opened with vlc instead of totem? What if you want cd’s to be opened with exaile instead of rythmbox? If you search for files mp3′s get opened with totem, … all these things can’t be changed with the provided GUI nor with “gconf-editor”.
I hope this will be “fixed” in the next Ubuntu release this October.