The people that use CQ today build highly visible marketing applications where content changes are common.  CQ provides an authoring environment that makes it easy for non-technical resources to change out images, text and other content on a website.  The content is centrally managed in the CRX (Content Repository Extreme) and authors can edit pages in a pre-production environment.

From a pure J2EE developer experience, the framework feels like a combination of new and old technologies.  The developer creates JSP templates that define the layout of the web page.  There are JSP components that you can directly reference in the template or make available to the authors to drag and drop on a page.  CQ relies on a RESTful web application container.  CQ uses an OSGi console to add back end java services for handling post requests, accessing business logic and/or integration with external systems.  There is plenty of cool, non-mainstream technologies mixed in with traditional JSPs to provide an interesting product.

So far the framework has a lot of potential.  The administration tools are excellent for authors making it easy to edit content.  The custom Eclipse IDE has a lot to offer but doesn't support plugins.  I can see why this platform is very popular in marketing circles because of it's author friendly experience.  From a J2EE developer standpoint the framework may feel a little constraining and you may want to consider using only CRX for sites that require more dynamic content.