Currently Being ModeratedJan 2, 2013 6:41 PM (in response to newmediadave1)
I'm having a similiar problem and I'm sure it didn't happen with the previous version of iMovie. I'm importing images from Aperture and building both SD & HD slideshows (for iDVD & and a stand-alone MP4/MOV video) and adding the images & HD video to the DVD assets manually.
For me, the issue isn't the preview quality as revealed in the finder (I cleared the Aperture previews and reset them to unlimited so the file sizes are several MBs at full resolution) but iMovie seems to degrade the quality on both it's full-screen playback and any exported HD video.
I can't seem to find any setting in iMovie that explains the degradation so I'm assuming it's just poor downscaling but any help would be gratefully appreciated.