One thing to keep in mind is that, at least from my experience, all of the DV files I've recorded in iMovie need audio rendering in order to be fully usable in Final Cut. What I do to avoid this is find the DV files within the iMovie project, then use QTAmateur to batch export the clips as a Quicktime movie using DV as the codec. Final Cut takes it just fine, then. One thing to keep in mind is that there may be very minor quality loss (I've compared frames from the original and exported DV files, and when you zoom in really far you can notice very slight degradation, but I don't think it's noticeable in regular usage). This may be due to the fact that the bitrate for iMovie DV files is a lot higher than the bitrate that Final Cut puts out (~50MB/sec vs ~30MB/sec).