iMovie 08 won't install on my 1.5GHz PowerBook G4. Plus I don't need to edit anything, just transcode. ffmpeg did the trick perfectly. I really don't know of any commercial solution on the Mac that would allow the same type of control, support the same number of formats and produce the same quality results.

I'm going to try applying the latest updates for iLife and will give iDVD another shot with the interim MPEG-2 files output by ffempeg. I'm curious if iDVD will allow me to stick 4 of them onto a single disc without screwing them up.