Mark Pilgrim has a thorough post explaining his move to open formats. If you care about preserving your data, you should go and read it. On one small point I may be able to give some advice. Mark said:
[I spent] Years of creating content, most recently video content in iMovie. Home movies of my children being born and growing up, heavily edited and burned to DVD and distributed to friends and family. Plus a few screencasts and some other odd video projects I’ve never released. Years of tagging and organizing an ever-growing collection of music, photos, and multimedia. I’ve now exported all my home movies as .DV files — one for the final product, one for all the unused clips. All other edits are lost. All editability is lost.
Mark, have a look at the QuickTime format. It is published and open, has been substantially the same for 15 years, and iMovie (finally) stores it's edit lists in it.