I just noticed before heading out the door that iSilo 4.0 has been released as a beta along with iSiloX/C. Updates in 4.0 include: font support (using FontBucket fonts, their own Font Silo format, and FontHack fonts), support for additional encodings, support for lossy compression, support for vCard and vCalender elements, and support for "inline document drop-down menus."
iSilo
http://www.isilo.com
iSiloX/C
http://www.isilox.com
Information on the new beta
http://www.isilo.com/info/beta/changes.htm