It's been quite a while since I used iMovie, so i could be remembering incorrectly or out of date.
My impression was that iMovie was more about combining pre-recorded clips and sound snippets with transitions and effects, but you couldn't say trim out a section of a clip, cut a larger movie into smaller clips or rip and transcode the audio from one clip to another.
I suppose they could add those features to iMovie if they're not there already. It's kind of a shame though, the quicktime pro player was the last hold out from being iLifed. The interface is simple and straightforward, cutting and pasting quick clips, grabbing sound bites or splicing things together is quick and easy without being to dumbed down.