The new properties will be available with Q2 2016. 

The issue is reproduced only with GroupRenderMode="Flat".

ClipboardCopyMode enumeration will expose a new property - SkipNullOrEmptyValue - setting whether null/empty value will be copied or not. Thus if copying cells from a column with multiple empty values, will not have a result in the pasted text, but rather be skipped.

The functionality is documented at http://docs.telerik.com/devtools/wpf/controls/radgridview/filtering/icolumn-filter-descriptors and for the time being the functionality can be achieved by implementing an attached behavior. 

I would like to be bale to modify at once several cells of a GridViewComboBoxColumn, when using the common ItemsSourceBinding for all rows (in my GridView, the selection ​is: SelectionMode="Multiple" SelectionUnit="FullRow").
So I would like for the selected rows to apply the same value as the edited cell.

GridViewHeaderCell are not draggable when RadGridView is hosted in DropDownButton.DropDownContent. Trying to drag a cell does not trigger drag events.

The problem should be resolved with lib version 2015.3.1012.

The designer crashes with this exception:
InvalidOperationException: 'GridViewColumnGroupRow' TargetType does not match type of element 'GridViewColumnGroupRow'.

See the attached screenshot. It's from a new project, after clean and rebuild.

Visual studio: 2015
Telerik UI for wpf: 2015.2
Implicit styles, Windows8 theme.

* The problem is not theme specific. As a workaround, use no xaml binaries instead of xaml files.