Adobe Experience Manager (AEM) is hands down the best Content Management System (CMS) I've had the pleasure of working with.
The ease with which you can put together layouts and pages without being tied to a particular grid layout enables you to produce stunning content in rapid time frames. No wonder it is utilised by publishers like http://www.telegraph.co.uk
If being author friendly is its key strength then development is its Achilles heel. You'll need deep pockets to be able to develop AEM to fit your business model, and there is no publically available repository of modules and plugins like you see with mainstream open source CMS like Joomla or Drupal.
However, once you've built your library of reusable components AEM becomes the most powerful CMS yet developed, and it is no wonder that Digital Agencies are pressing it into service for their clients. Being able to easily find and display images using the Digital Asset Manager (DAM) means that your authors can quickly search for and use graphical elements without having to resort to laborious FTP reducing producer training times.
AEM is the market leading product with a market leading price tag to match.