Change the selection on MouseLeftButtonUp instead of MouseLeftButtonDown.

Add a possibility to disable selection of RadTreeViewItem.

Support CommandBindings.

The item is Completed =>
RadTreeViewitem is ICommnadSource since 2011. 
RadTreeViewItem already has Command property, the command fires on mouse click.

Show tooltip when node (the Header of the RadTreeViewiItem) is clipped.

You can check a possible implementation in this SDK sample:
https://github.com/telerik/xaml-sdk/tree/master/TreeView/ShowTooltipWhenNodeIsClipped 

Allow cancelling a drag operation originating from certain items - basically the customers need to disable the drag operation on some items.
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Here is a possible solution with handling DragInitialize
 
DragDropManager.AddDragInitializeHandler(this.tree, this.OnDragInitialize, true);

 private void OnDragInit(object sender, DragInitializeEventArgs e)
        {
            if (((e.OriginalSource as RadTreeViewItem).Header == "B1")
            {
                e.Data = null;
                e.DragVisual = null;
            }

When you tab through your application you can observe that when the focus moves to the TreeView it will focus the first TreeViewItem. However, when you change the ItemsSource collection of the TreeView at run-time you won't be able to tab through the TreeView or its first TreeViewItem at all.

Fixed in LIB version: 2014.2.0915

Create localization resources for the DropActionText in the TreeViewDragVisual element. The localization resources should work as the TextDropAfter, TextDropBefore, TextDropIn and TextDropRoot properties used to work in the Legacy mode of the RadTreeView DragDrop.

Consider replacing the current touch gesture which starts drag operation. Now the gesture (tab and hold + move up) is not very intuitive. 

With Q2 2015 Release the DragDrop on touch device will work the following way. Hold down the finger on RadTreeViewItem, TouchIndicator circle appears and then you can move your finger to start the dragging.

Select a RadTreeViewItem with MOuse and in SelectionChaged event handler disable the RadTreeView. Then when you enable it programatically, the SelectedItems's foreground is wrong.

Available in LIB Version: 2015.2.720.

Setting these properties in the Legacy mode works as expected. The NEW DND mode will be the default one in Q2 2014.