CellEditorDisplayConditions.Always, MouseOverCell, and MouseOverRow will only function in the case where Xceed.Grid.Editors.CellEditorManager.CreateControlMode is set to CreateControlMode.ClonedInstance.
Setting this property to CellEditorDisplayConditions.Always will decrease performance.
The value returned by your implementation of DefaultCellEditorDisplayConditions should not be dynamic.
Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2