I can't offer a definitive answer either because I don't have a release
version of the product. But as far as I can tell, you should be able to
insert the value of a text (i.e. as opposed to image) Sharepoint property
using a content control (via Insert|Quick Parts|Document Property)

These document properties are not the same as Office document properties and
the resulting object in the document is not a traditional DOCPROPERTY field,
but a content control (i.e. more like an online form field or
old-style Toolbox control. You may need to set the properties of the content
control if you don't want the user to be able to edit the values directly in
the document, if SharePoint doesn't enforce that itself.

Also, you can only insert content controls in .docx type documents - if you
save as Word 97-2003 .doc format, Word will replace the controls by their
text values., and the list of Document Properties under Quick Parts will be
greyed out.

Peter Jamieson