Placing the RadGridView control inside a PanelBarItem element does not display all of its rows when the GroupRenderMode is Flat.

A workaround for this is to place the RadGridView element inside a Grid layout and create a new RowDefinition with Height="Auto". 

<telerik:RadPanelBarItem>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <telerik:RadGridView/>
    </Grid>
</telerik:RadPanelBarItem>

Setting a RadGridView element instance as content for a RadPanelBarItem, causes the RadGridView to not show all of its columns.

As a workaround to this, you could set the IsScrollViewerInsideItemsEnabled property of the RadPanelBar element, to True, and you could control the expanded length of the PanelBarItem which holds the RadGridView instance. This could be done by utilizing the ExpandedLength property.

Add a ScrollViewer to the PanelBarItem ControlTemplate

Allow resizing of PanelBarItems. http://www.telerik.com/community/forums/wpf/panelbar/resize-capabilities-to-radpanelbaritems.aspx

When using an ItemContainerStyle on the second(non-root) BarItems, the Background doesn`t apply

When a control is nested in a RadPanelItem, it is wrapped in another RadPanelBarItem. The DataContext of the second level item is not inherited correctly. As a workaround, you can bind directly to the element which holds the DataContext with an ElementName binding. 

Update the ExpandMode property to allow zero, one or zero, one ,and multiple expanded items.

Implement IsExpandOnDblClickEnabled logic

ExpandAll/Collapse issues, Child RadPanelbarItem is resized incorecctly

PanelBarItem with no Items is initially expanded when its IsExpanded property is data bound

If the RadPanelBar Orientation is Horizontal, a RadHtmlPlaceHolder cannot be displayed inside a RadPanelBarItem

ICommandSource for RadPanelBarItem, using the same principle like RadMenuItem, since RadPanelBar is mostly used as a menu.

The IsTabStop is set to false in all RadPanelBarItems and set to true in the textboxes in the Items of the PanelBarItems. When tab navigating the RadPanelBarItems get focused, in Silverlight they don`t.

When the RadPanelBar is oriented Horizontally , The ScrollViewer does not work when the mouse wheel button is used.