Setting Button, TextBlock, TextBox or any other UI Element as a Header of RadRibbonGroup produces a runtime exception: The Element is Already Child of another visual.

When UserControls are dynamically added in the RibbonView Items collection, they are displayed as RibbonTab Headers. Instead they should create a RibbonTab collection where each control represents the content of a RibbonTab.

UPDATE: An implicit style can not be applied on derived controls as their TargetType is different than the one defined in the implicit style. Basically if you set the style implicitly, the style is applied only on the types that match the TargetType exactly and not on elements derived from the TargetType value. You can find more information on the topic in the remarks section of the Style property definition: http://msdn.microsoft.com/en-us/library/system.windows.style%28VS.95%29.aspx

This is why in order to apply a Telerik predefined style on a UserControl deriving from RadRibbonTab, you  need to add a Style targeting the UserControl type in the Resources of the application. It is best to define that style after merging the Telerik ResourseDictionaries so that you can base the UserControl Style on the predefined "RadRibbonTabStyle".

typically users consider keys like Shift,Ctrl,ALT to be a single key even though they are on the keyboard left and right.

When you set the Content and the Image properties of the RadGalleryItem, they get on top of each other.

There is a flickering when the active ContextualGroup is changed - the RibbonView first selects the non-contextual main tab before it switches to the according contextual tab. The flickering can't be observed every time.

There are three errors for missing icons when implicit themes are used:
Resource '/Telerik.Windows.Controls.RibbonView;component/HelpIcon.png' was not found.
Resource '/Telerik.Windows.Controls.RibbonView;component/RibbonGalleryCollapsedIcon.png' was not f

Support easy customization of screen tip duration.

We have a RadRibbonView with enabled KeyTips and a RadComboBox control below it.
We focus the RadComboBox and press "Alt + DownArrow". As a result the the RadComboBox is opened and immediately closed and KeyTip is activated and shown and the coressponding RadRibbonTab gets the focus. The expected result is that the RadComboBox is opened, remains opened and no KeyTips are activated.

Expose an event where the key combinations that (don't)show the KeyTips can be customized.

Expose a property through which the TabContentPopup IsOpen state can be programatically controlled. This feature should allow the implementation of a scenario where the TabContentPopup is opened when hovering over the tab.

Declined: The current API of the RadRibbonView allow the users to control MinimizedPopup. A sample application is attached demonstrating how the Popup can me controlled

Available in LIB version: 2015.1.0604

When a view doesn't specify DesignHeight/Width, the RibbonView throws design-time exception if it contains ContextualGroups.

Expose a property to control the visibility of the background behind the RibbonTab.Headers

UPDATE: The RadRibbonView's Background property can be used to set a color behind the RadRibbonTabs

Implicit style doesn't apply on RadRibbonTabs which are added via PRISM.

UPDATE: An implicit style can not be applied on derived controls as their TargetType is different than the one defined in the implicit style. Basically if you set the style implicitly, the style is applied only on the types that match the TargetType exactly and not on elements derived from the TargetType value. You can find more information on the topic in the remarks section of the Style property definition: http://msdn.microsoft.com/en-us/library/system.windows.style%28VS.95%29.aspx

This is why in order to apply a Telerik predefined style on a UserControl deriving from RadRibbonTab, you  need to add a Style targeting the UserControl type in the Resources of the application. It is best to define that style after merging the Telerik ResourseDictionaries so that you can base the UserControl Style on the predefined "RadRibbonTabStyle".

If you delay adding a RibbonView in a RibbonWindow, the RibbonView is placed on top of the window, hiding its TitleBar.

Expose an IsActiveChanged event for the ContextualGroups

Will be available in Q1 2015 Release.

When both Command and IsEnabled of RadRibbonBackstage are bound, the Command has Higher priority. This is inconsistency with the behavior of Buttons and RadButtons. The RadRibbonBackStageItems should work like RadButtons.

The KeyTips of RadMenuItems go behind the menu when hovering over the RadMenuItem. This issue seems to be related to the ScreenTip/ToolTip settings applied on the RadMenuItems - if no such settings are applied, the issue cannot be reproduced.
The Tooltip popup is placed over the KeyTips popup.

When a style is applied on the QAT, changing its position opens its popup menu unexpectedly. The style doesn't have to be customized, the issue is reproducable with the default OfficeBlack style of the control.

Currently the Backstage support keyboard navigation only if the the RadBackstageItems have their IsSelectable property set to true. The keyboard support should be extended to support BackstageItems that have IsSelectable=false.

Will be available in Q2 2015 Release.