When the RadPanelBarItem is expanded the arrow in its header is not consistent across themes. We should make sure that the arrow points in the same direction in all themes. 

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. 

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

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.

Add a ScrollViewer to the PanelBarItem ControlTemplate

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

Current behavior:

http://admin.telerik.com/Images/editor/Silverlight/PanelBar/31-08-10/current_outcome.png

Expected behavior:

http://admin.telerik.com/Images/editor/Silverlight/PanelBar/31-08-10/desired_outcome.png

Possbility to have PanelBarItems with fixed height and other PanelBarItems that take the rest of the available height equally

Exception is thrown in the designer when threre are many items in the PanelBar control.