This is a much higher- end scanner designed for professional prepress applications. It sells for a little over $10K. It is the litttle brother of the Flextight Precision II which has been widely acclaimed in prepress magazines and news groups. The main difference between the two is that the Flextight Photo does not have adjustable optics and is therefore fixed at an optical resolution of 3200 DPI. This also limits the maximum size of the scanned image to 6cm wide (perfect for medium format). 

It also connects to the computer using a SCSI interface. It does not do multiple passes, but the quality of the scans is noticably higher than with the Nikon. I assume this is due to some combination of optics, CCD quality, motor drive accuracy, and power line filtering. 

Scans are significantly faster than the Nikon (comparing the single pass from the Imacon and the 16x pass of the Nikon and yield better results. The prescan pass is also significantly faster and the software is easier to use to get the highest quality scan.

The Imacon uses a fairly ingenious media holder made out of stamped metal with a rubberized magnet to hold the media in place. The rubberized magnet is lifted up to place the negative or transparency over the opening. The magnet is then lowered to hold the edges of the media (negative or transparency). Different holders can be made for different film formats. It comes with holders for 35mm and various medium format sizes, but additional custom holders can be ordered for a nominal charge.

The biggest disadvantage of this approach is that 35mm transparencies must be scanned unmounted. However, since the film is bent slightly (similar to the way a drum scanner works), film flatness is much easier to guarantee and the resulting scan is exceptionally sharp.

I don't have any direct comparisons with other scanners yet, but suffice it to say that I can create a 30"x40" enlargement from a 645 scan that looks stunning.