I had a question about this too. I'm trying to select clips from two different cameras but it's nearly impossible to keep them in sync in iMovie because, as far as I can tell, there's no way to reveal the timestamp as you rollover your footage. If I could at least tell how far along I was while scrubbing, then I could manually select the (more or less) exact clips I need.
Oh well, time to download the trial of FCPX and see how I like that. I have a feeling my wallet is soon going to be $300 lighter...