It may be a day late, but it’s well worth the wait. You can download it here - http://cesium.agi.com/downloads.html
The biggest news of this release is our new packaging, but we also have plenty of bug fixes and several new widgets. Check out the blog post for more information: http://cesium.agi.com/2013/04/01/Cesium-version-b15-released/
Regarding our new release packaging, we are very interested in feedback from the community. Our goal was to make it easy for new users to get up and running quickly, as well as make it easy for the user to decide which package is right for them. Feel free to respond to this post, or comment on the blog post if you have any feedback.