The Plone.net site has a very good case study on Discover Magazine's migration to Plone. The Discover Magazine site looks like a model magazine site: clean, careful presentation; lots of imagery and multi-media; registration only content; and synergy with the print edition. The article covers how Plone is used to manage content, user adoption, performance, integration with 3rd party applications, and content migration. It's a very worthy read if you are considering Plone for your news or magazine site.
I am also encouraged to see that the Plone.net site (which is targeted to business users) is filling up with content. There are 34 case studies and the Plone sites directory contains 1,442 entries. I know that this was a key strategy to achieve the goal of increasing awareness about Plone and it is impressive to see the progress they have made.