RadTreeViewItemEditedEventArgs returns the same object in the OldValue and NewValue properties when using the Edited event.

The items of the RadTreeView control do not behave correctly in a touch scenario when expanding/collapsing them.

A possible workaround for this behavior would be to set the TouchManager.ShouldSuspendMousePromotion attached property to True on the RadTreeView control instance.

RadTreeView with virtualization turned on, defines HierarchicalDataTemplates for its items. 

In the template, the root panel is 32 pixels (or higher than the default TreeViewItemHeight - 24 px in OfficeBlackTheme). Scrolling the treeview, then maximizing the wpf window results in misplaced / incorrect height of treeviewitems.

Possible workaround:
Set the MinHeight property of RadTreeViewItem so that all its header content fits. Then set the item's VerticalContentAlignment to Stretch
        <Style TargetType="telerik:RadTreeViewItem">
                         <Setter Property="MinHeight" Value="48" />
                        <Setter Property="VerticalContentAlignment" Value="Stretch" />
                   </Style>

Also following settings might help:
   - setting fixed width/height of the RadTreeView
   - setting ChildDefaultLength to 48 of every TreeviewPanel:
			<telerik:RadTreeView.ItemsPanel>
				<ItemsPanelTemplate>
					<telerik:TreeViewPanel ChildDefaultLength="48" />
				</ItemsPanelTemplate>
			</telerik:RadTreeView.ItemsPanel>
        <Style x:Key="ItemContainerStyle" TargetType="{x:Type telerik:RadTreeViewItem}">
			<Setter Property="ItemsPanel">
				<Setter.Value>
					<ItemsPanelTemplate>
						<telerik:TreeViewPanel ChildDefaultLength="48" />
					</ItemsPanelTemplate>
				</Setter.Value>
			</Setter>

SelectedItems collection not updated when items are removed

When you reorder the collection very fast an exception is thrown. This is reproducible when the UI virtualization is enabled with its virtualization mode set to Recycling, and an item is selected. Also, you can observe some missing items glitches instead of the exception. To reproduce this you can call the ObservableCollection's Move() method several times in a single method (see the attached project). 

In this case also a NullReferenceException is thrown sometimes instead of the InvalidOperationException.

To work this around delay the reordering calls so that the treeview has time to properly measure and arrange itself. For example:

Items.Move(10, 2);
Application.Current.Dispatcher.BeginInvoke(new Action(() =>
{
Items.Move(10, 2);
}), System.Windows.Threading.DispatcherPriority.Background);

System.Windows.Media.Animation Warning is apparent during DragDrop in the TreeView in WPF. 

The scroll position resets when the measure of the treeview panel is fired for some reason.

For example, when the RadTreeView is placed inside a RadPanelBarItem and the RadPanelBar's ScrollViewer is disabled, resizing the RadPanelBar resets the RadTreeView scroll position. 

When expanding all items with a horizontal scrollbar the last item is hidden by the scrollbar. As a workaround, you can set the IsVirtualizing property of the RadTreeView to True.

Generated item cache is not cleared properly. This leads to memory leaking when items are virtualized and realized. 

As a workaround you can set the IsVisualCacheEnabled property of the TreeViewPanel to False. Note that this will work only in Recycling VirtualizationMode.

<telerik:RadTreeView.ItemsPanel>
    <ItemsPanelTemplate>
        <telerik:TreeViewPanel IsVisualCacheEnabled="False" />
    </ItemsPanelTemplate>
</telerik:RadTreeView.ItemsPanel>

When IsVirtulizing is set to true and there are many items in the tree view pressing several times PageUp key brings the view port to the beginning of the tree rather to the previous page.

Rendering issues occure when using Hierarchical virtualization mode and bring into view.
The issue is hit in both platforms - WPF and Silverlight. 

When placed in grid column with Auto width and had its own width set to Auto, the RadTreeView does not scroll.

When the TreeView's ScrollViewer is Visible, changing the tree's width to 0 them back to Auto breaks the scrolling function of the ScrollViewer.
The workaround is to make the TreeView Collapsed before setting the Width to 0 and make it Visible before setting the Width back to Auto.

Another workaround: Use visibility instead of Width=0.

SelectedItem property should not accept RadTreeViewItem objects when is data bound.

Reason for decline:

Setting a non-default value to the RadTreeView ItemsIndent property disarranges the lines

Scenario: Databound TreeView with IsSelected bindings between item and container. Adding a selected data object to the ItemsSource does not fire the Selected event.

The vertical scroll cannot be moved via the mouse wheel or by clicking on the scrollbar's thumb after the End key is pressed. This is reproducible ONLY if the UI virtualization is enabled and if there are many items (500-1000+).

The TreeViewItems are expanded and collapsed on MouseLeftButtonUp which leads to an expand/collapse operation even if the MouseLeftButtonDown event was fired by another element. This can be easility reproduced if you hold down the mouse left button over any element outside the RadTreeView and then releasing it over any RadTreeViewItem when the RadTreeView IsExpandOnSingleClickEnabled is True.

It can also be reprorduced with the following steps:
1) left click on a node and hold the mouse button down
2) release the mouse when over a non-selected node that has children.
The result is expanding/collapsing the unselected node.

Use virtualization in hierarchical mode. Select a RadTreeViewItem that has parent. Move it somewhere in the source collection of the parent programmatically - reorder or sort. The item will remain in Museover State forever.

Perform the same steps with Recycling mode, there might be missing RadtreeViewItems (not rendered at all) after the sort / reorder operation.

TreeView Virtualization Mode is Recycling (the default one). In the ItemTemplate there is a RichTextBox with HtmlFormatProvider. Changing ItemsSource of the TreeView runtime produces null reference exception in TreeViewPanel.CleanupRange().
The Exception comes from the RecyclingItemContainerGenerator.Recycle method (http://msdn.microsoft.com/en-us/library/cc452208(v=vs.110).aspx). 
As a workaround if applicable, user can use the HierarchicalVirtualization mode:
    <telerik:RadTreeView  telerik:TreeViewPanel.TreeVirtualizationMode="Hierarchical"