I also would like the DjVu support. DjVu is *the* format of choice in certain circles (academic, see
http://www.ulib.org/ or in Russia, etc.). It is possible to make a scan DjVu that will be ten times smaller of an equivalent quality scan PDF. The problem is that the format is not promoted and lacks interest from the developer (i.e. no muscle to back it up) and some tools are costly (although there are open source alternatives).
By the way, the best DjVu viewer is
http://windjview.sourceforge.net/
See a comparison of djvu and pdf here:
http://c-sharp-snippets.blogspot.com...00-in-pdf.html