SQL Developer Data Modeling is now an early adopter release, available for download from OTN. Before you can download, you need to complete a a short questionnaire. This also gives you access to a feedback application. The SQL Developer team will review you feedback and respond with help or log bugs and enhancements.
FAQ on Early Adopter Release (Use this link to add your gained experience on SQl Developer. - Do not post questions here without answers, use the feedback app for that)