I think iM08 displays the mini movie it creates for skimming. That quality likely isn't as nice as the original DV file. Also, the size of the playback image can have an affect, so make those the same when comparing.
I'd just create a small project clip, and export to QuickTime in the Apple Intermediate Codec format and look at the result in QiuckTime. The export would use the DV source, not the mini skimming movie, so it should look nice.