Parse event of the property binding is not fired when you change the ToggleState value of RadToggleButton:

Workaround:

private void Form1_Shown(object sender, EventArgs e)
		{
            Binding b = new Binding("ToggleState", vm, "IsToggleSet", true, DataSourceUpdateMode.OnPropertyChanged);
			b.Format += new ConvertEventHandler(b_Format);
			b.Parse += new ConvertEventHandler(b_Parse);
			radToggleButton1.DataBindings.Add(b);
		}

		void b_Parse(object sender, ConvertEventArgs e)
		{
			if (e.DesiredType != typeof(bool) || !(e.Value is ToggleState))
				return;

			ToggleState state = (ToggleState)e.Value;
			e.Value = (state == ToggleState.On) ? true : false;
		}

		void b_Format(object sender, ConvertEventArgs e)
		{
			if (e.DesiredType != typeof(ToggleState) || !(e.Value is bool))
				return;

			bool isToggleOn = (bool)e.Value;
			e.Value = isToggleOn ? ToggleState.On : ToggleState.Off;
		}

RadCheckBox can be checked by the right mouse button

Sometimes after rapid clicking on RadSplitButton, its DropDown stops closing when the user clicks outside it.

Pressing backspace key in ComboBox element added to a RadDropDownButton closes that popup box and doesn't allow you to do any modification

RadRadioButton behaves differently from the Microsoft RadioButton in terms of keyboard navigation.

The mouse right button should not fire the click event of the radbutton. A check should be performed, which only fires the click in case it was clicked by the left button. Possibly, this check should be performed at the TPF level, so it will be available for all controls.

The theme is not applied properly when the button is toggled off.