The TreeViewItem should display the type name as well as the item's Header, e.g: "Telerik.Windows.Controls.TreeViewItem Header:Header Content Items.Count:20"
Rendering issues occur when using Hierarchical virtualization mode and bring into view several times. The Headers of some items appear over other Headers. The feedback item is declined due to duplication with the one below: http://feedback.telerik.com/Project/143/Feedback/Details/113680-treeview-rendering-issues-when-using-hierarchical-virtualization-mode-and-bring Please follow it instead.
Users often need to customize only the Content of the TreeViewDragVisual. The built-in logic for displaying Drop Target Template (Drop Inside X, Drop after Y) is well accepted. However, there is no easy way to customize the Content of the DragVisual only , preserving the built in logic. If you create entirely new DragVisual much more code is needed to set up all scenarios. Will be available in Q2 2015 Release.