I'm trying to grasp what Radiant CMS is. I went through the demo. My initial impression is that Radiant a page management system more concerned with structure than content. In contrast, a CMS like Drupal is focused on content. That is the basic unit of management is content be it an artricle, product, blog entry, video clip, a recipe ...
Radiant is focused on the developer who thinks in pages instead of the end user who thinks in types of content. The markup supports this. Most end users would be confused with liquid templates. In general, the Ruby CMS I researched do the same thing with their own twist. I wonder if any Ruby CMS will ever reach the status of Drupal because of the difference in approach. That is not to say Drupal is the ultimate CMS. There are times when I want to create a page in Drupal and life would be easier if Drupal behaved like Radiant. Is the lesson learned to not put everything in one admin and mix concerns? How about a separate admin area for end users where, for example, a blog entry is nothing more than one or more paragraphs. The existing admin would be used by developers and designers to create layouts and page prototypes which can be selected by end users. Does this make sense at all?
