This package has significantly improved in the past few versions, and is a good choice for people who have to maintain large sites.
Educational pricing is extremely competitive.
Nice multimedia and Java support, too. Now in version 1.2. Not yet widely adopted, this is a tool for the future. Very useful and current list of the major SGML and XML authoring packages, with links to reviews and manufacturer home pages. XLink XPointer SPDL CGM ISO-HTML several others.