Additional resources
As this is still in beta, there are not too many official resources that have been written about the UI system as of this writing, but there are some video lessons that are available at http://unity3d.com/learn/tutorials/modules/beginner/ui.
However, the Unity forums have a very active community, including Unity developers, who are happy to answer questions that developers may have. There is a specific place to ask about the new UI system at http://forum.unity3d.com/forums/developer-preview-4-6-beta.60/.
There is also a set of example projects, which have a number of examples showing how to use some of the aspects of the system at http://forum.unity3d.com/threads/ui-example-project.263418/#post-1744107.
For those interested in ...
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