In that way it will be easy to set the popup animation to be slide, fade or scroll without setting a custom template. 

Available in R1 2017 Release

Clicking on the RadSplitButton in XAML opens the designer unexpectedly

Available in LIB version: 2015.1.0309

The native radio button supports validation. Implement validation for the RadRadioButton

An updated button that appears and acts like a hyperlink but is really a button with no borders but respects the enabled / disabled and all the visual states. 

 *  link should be disabled / grayed out if not enabled or if command guard is not enabled 
 *  could manage the 'visited' as a pressed (not interested in that for me, I just like the simple visual).
 *  the samples/demos homeview provides a nice example where the long text is highlighted and presents the hand icon. The re-styling is however 6 pages long and cumbersome to copy as it references other parts of the sample project (I tried)

Close the DropDown popup when clicking on the DropDownContent in DropDownButton.

Available in R3 2016 Official Release.

A button with state that looks like a switch.

We have created a SDK sample demonstrates how to style a RadToggleButton to look like a Toggle-Switch button. 
You can find the example in out SDK repository(https://github.com/telerik/xaml-sdk/tree/master/Buttons/ToggleSwitchButton)