Drupal is a great open source CMS. One of the reasons I like it is the strong community around the platform. There are many different modules available for all kinds of purposes, ranging from forums to integration with salesforce.com. Secondly, many vendors releasing new products are creating plugins for this platform to generate traction, such as Kaltura , OpenX and Mobify.me. With this kind of community support, an open source CMS solutions have a leg up in how easily new features or trends can be incorporated in a web site. Other open source solutions like WordPress have these same benefits as well.
It is interesting to see that there is now also some community traction around enhancing the user experience of the Drupal administration functionality. This blog post shows some great ideas around improvements than can be made, while still building upon the foundation that is currently in place. The Drupal 7 User Experience project outlines similar strong ideas. Incorporating ajax functionality such as drag and drop within the admin user interface would make Drupal a CMS that can become much more user friendly, allowing business users to really control their site.