One requirement I have for WCM is that the content template definitions lend themselves to reuse. Many of the commercial WCM offerings today are very limited in this ability. In sites where hundreds of templates are implemented you wind up with a maintenance nightmare.
For example, if I have a chunk in a piece of web content that includes name, address, city, and state, I ought to only have to declare that chunk once and be able to easily reuse it across many templates.
Same story for presentation. If I write a chunk of XSLT that transforms the address XML into HTML, I only want to define that XSLT once and then use something like xsl-include to refer to it.
Jeff