This is a fairly minor point, as the workaround is simply to change image mode from 16 to 8 bit, but it might make sense to have the exporter process 16-bit images directly, doing whatever conversions make sense for the output type.
I just posted a comparison of HD View and Silverlight output and viewers here: http://www.bstorage.com/Photo/DeepZoom/MalteseFalcon/
Some other San Francisco pano images of various sizes here: http://www.bstorage.com/Photo/DeepZoom/
Bill