When browsing an ezdemo install in the backoffice, the used templates don't match the content classes.
They're most likely default for the plain install. For instance, on Article, the location or author aren't displayed.
A minimum would be to use the standard node/view/full.tpl template. This would at least ensure that content can be previewed.
Ideally, we would write simple templates for the ezdemo classes, at least the most used ones (article, etc).