Personally, I've been running Ubuntu alongside MorphOS on a PPC Mac for some time now. Works great. More than fast enough and better looking than OSX.
I am getting ready to set up a new hard drive with a triple boot of MorphOS2.7, MacOSX 10.5.8, and Ubuntu 10.10 PPC (or another flavor of Linux if someone can convince me of the advantages of any other Linux distribution over the Ubuntu 10.10 distro).
Can you suggest which method of installation works best to achieve the above, I mean which OS should I install first, which one second and which last? The hard drive I am putting these on is 320gb in size and I would like to load up a lot of movies & music on it that I can access from all three OSes without having to have duplicate movie & music files on every partition, so I would also like partitioning and partition formatting suggestions. I have paid for the keyfile for the Ice File System and also own PSF3 commercial, but do not have to use either of them if they are not suggested.