it seems like I just discovered a little design issue. The AnimatedDockPanel obviously does not have a ContentProperty-Attribute attatched. When I add various controls to the panel directly, the UI designer shows an error telling me, that AnimatedDockPanel doesn't support direct content.
It does compile fine and obviously works, but marks the whole part in the XAML underlined. Explicitly adding content in "<views:AnimatedDockPanel.Children></...>" does work, though.
You might want to check if the Attribute is set, else it would be nice if you fixed that problem. Not much of a problem, but a little design imperfection.
PS: You might want to add Windows 10 to the platforms list in the forums ;)