Is is possible with GridViewComboBoxColumn to apply the selected value on combobox select.
Now I have the following combobox column and the selected value is set to the viewmodel when the cell lose focus:
<telerik:GridViewComboBoxColumn Header="header text" ItemsSourceBinding="{Binding Actions}" DataMemberBinding="{Binding Action, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" DisplayMemberPath="NameDisp" EditTriggers="CellClick" />