I have been using the multiple exposure feature of the Silverfast to rescan some high contrast negatives. It does a pretty good job, but I found one problem. Sometimes you get artifacts in Siverfast multiple pass scans, probably because of movement of the negative. These are easy to spot - there is clearly a problem all over the scan. With ME I have found that you can isolated artifacts that look like doubling or scalloping on a few high contrast edges. If do life size dust scans you will probably see them, but I missed them on a couple of images because they in areas of the image where it was hard to tell if they were artifacts or detail. Once I figured out what was happening, it was easy to spot on scans that just had few "funny" spots.